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SERVICE
MANUAL
Models
EX13,17,21,27
SP170,SP210
EX21 Electronic Fuel Injection
ENGINES
PUB-ES1934
Rev. 08/09
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CONTENTS
Section
Title
Page
1. SPECIFICATIONS ...................................................................................................... 1
2. PERFORMANCE ...................................................................................................... 2
3. FEATURES ............................................................................................................... 7
4. GENERAL DESCRIPTION OF ENGINE COMPONENTS........................................ 8
5. DISASSEMBLY AND REASSEMBLY .................................................................... 14
5-1 PREPARATIONS AND PRECAUTIONS............................................................ 14
5-2 SPECIAL TOOLS .............................................................................................. 14
5-3 DISASSEMBLY PROCEDURE.......................................................................... 15
5-4 REASSEMBLY PROCEDURE........................................................................... 29
6. ENGINE OIL ........................................................................................................... 47
7. MAGNETO .............................................................................................................. 48
8. WIRING DIAGRAM................................................................................................. 51
9. ELECTRIC STARTER............................................................................................. 53
10. OIL SENSOR .......................................................................................................... 55
11. AUTOMATIC DECOMPRESSION SYSTEM........................................................... 56
12. CARBURETOR....................................................................................................... 57
13. RECOIL STARTER ................................................................................................. 61
14. INSTALLATION ...................................................................................................... 66
15. TROUBLESHOOTING ............................................................................................ 68
16. STANDARD REPAIR TABLES ............................................................................... 74
15-1 STANDARD DIMENSIONS AND LIMITS OF USE ........................................... 74
15-2 TIGHTENING TORQUE .................................................................................... 80
17. MAINTENANCE AND STORAGE .......................................................................... 81
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1. SPECIFICATIONS
Model
EX13D
EX17D
EX21D
EX27D
Air-Cooled, 4-Cycle, Slant Single-Cylinder,
Horizontal P.T.O. Shaft, OHC Gasoline Engine
Type
mm
58 x 48
67 x 48
67 x 60
75 x 60
Bore & Stroke
(in.)
(2.28 x 1.89)
(2.64 x 1.89)
(2.64 x 2.36)
(2.95 x 2.36)
ml
Piston Displacement
(cu.in.)
126
(7.69)
169
(10.31)
211
(12.87)
265
(16.17)
Compression Ratio
8.5
8.3
1.9(2.6)/3000
2.2(3.0)/3600
2.6(3.5)/3000
2.9(4.0)/3600
3.2(4.4)/3000
3.7(5.0)/3600
4.4(6.0)/3000
5.1(7.0)/3600
Continuous Output
Maximum Output
kW(HP)/r.p.m.
kW(HP)/r.p.m.
3.2(4.3)/4000
4.2(5.7)/4000
5.1(7.0)/4000
6.6(9.0)/4000
N m / r.p.m.
(kgf m / r.p.m.)
(ft lb. / r.p.m.)
8.1/2500
(0.83/2500)
(6.01/2500)
11.3/2500
(1.15/2500)
(8.34/2500
13.9/2500
(1.41/2500)
(10.26/2500
18.6/2500
(1.9/2500)
(13.74/2500
Maximum Torque
Direction of Rotation
Valve Arrangement
Cooling System
Counterclockwise as viewed from the P.T.O. shaft side
Overhead cam system
Forced air cooling system
Lubrication System
Splash lubrication system
Automobile engine oil ; Grade SE or higher (SG,SH or SJ in recomended)
SAE 10W-30-----Under ordinary atmospheric temperatures
SAE 5W-30-------In cold areas
Lubricant
Capacity of Lubricant
Carburetor
L
0.6
1.0
Horizontal draft, Float type
Automobile unleaded gasoline
Fuel
g/kW h
(g/HP h)
Fuel Consumption Rate
367 (270) at continuous rated output
Fuel Supply System
Fuel Tank Capacity
Ignition System
Spark Plug
Gravity type
3.6
L
2.7
6.1
Transistorized magneto
NGK BR-6HS (CHAMPION RL86C)
Charging Capacity
(Option)
V-A
-------------
1 2 -1 A , 3 A , 1 6 .7 A (Op ti o n )
Starting System
Governor System
Recoil starter
Recoil starter / Electric starter (Option)
Centrifugal flyweight system
kg
(lb.)
14
(30.87)
15
(33.08)
16
(35.28)
21
(46.31)
Dry Weight
mm
(in.)
297 x 341 x 318 304 x 354 x 335 311 x 366 x 335 351 x 420 x 410
(11.7x13.4x12.5) (12.0x13.9x13.2) (12.2x14.4x13.2) (13.8x16.5x16.1)
Dimensions (L x W x H)
Specifications are subject to change without notice.
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2. PERFORMANCE
2-1 MAXIMUM OUTPUT
The Maximum output is the output of an engine with its throttle valve fully opened and considering that all the
moving parts are properly broken in.
A new engine may not produce full maximum output while its moving parts are still not broken-in.
NOTE :
Power curves shown in the following charts are made in conformity with SAE internal combustion engine standard
test code J1349.
2-2 CONTINUOUS RATED OUTPUT
The continuous rated output is the output of an engine at optimum governed speed which is most favorable from
the view point of engin’s life and fuel consumption.
When the engine is installed on a certain equipment, it is recommended that the continuous output required
from the equipment to be kept below this continuous rated output.
2-3 MAXIMUM TORQUE
The maximum torque is the torque at the output shaft when the engine is producing maxim um output at a
specific r.p.m..
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2
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2-4 PERFORMANCE CURVES
EX13D
9.0
8.0
0.9
0.8
0.7
7.0
kW
4.0
MAXIMUM TORQUE
[HP]
5.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
MAXIMUM HORSEPOWER
4.0
3.0
2.0
1.0
0
CONTINUOUS
RATED HP
RECOMMENDED
HORSEPOWER
RANGE
2000
2400
2800
3200
3600
4000
REVOLUTION
r.p.m.
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EX17D
12.0
11.0
10.0
9.0
1.2
1.1
1.0
0.9
MAXIMUM TORQUE
kW
4.5
[HP]
6.0
MAXIMUM HORSEPOWER
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
5.0
4.0
3.0
2.0
1.0
0
CONTINUOUS
RATED HP
RECOMMENDED
HORSEPOWER
RANGE
2000
2400
2800
3200
3600
4000
REVOLUTION
r.p.m.
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EX21D
15.0
14.0
13.0
12.0
1.5
1.4
1.3
1.2
MAXIMUM TORQUE
kW
5.5
[PS]
7.0
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
MAXIMUM HORSEPOWER
6.0
5.0
4.0
3.0
2.0
1.0
0
CONTINUOUS
RATED HP
RECOMMENDED
HORSEPOWER
RANGE
0.5
0
2000
2400
2800
3200
3600
4000
REVOLUTION
r.p.m.
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5
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EX27D
19.0
18.0
17.0
16.0
15.0
1.9
1.8
1.7
1.6
1.5
MAXIMUM TORQUE
kW
7.0
[HP]
9.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
MAXIMUM HORSEPOWER
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0
CONTINUOUS
RATED HP
RECOMMENDED
HORSEPOWER
RANGE
2000
2400
2800
3200
3600
4000
REVOLUTION
r.p.m.
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3. FEATURES
3-1 EXTREMELY SILENT - SOFT TONE QUALITY
EX engines are 2dBA quieter and softer in tone than other engines in the same class.
This quiet and soft tone is achieved by:
- A reduction in mechanical noise realized by employing sophisticated OHC system.
- Employment of an optimized capacity Rigid Muffler.
3-2 EXTREMELY EASY START - NO KICK-BACK
Reliable Starting and Less Pulling Force are achieved by:
- Sophisticated Mechanical Compression Release System as well as newly designed Combustion Chamber.
- EX engines start instantly even at minus (-) 10 C, without any perceptible kick-back.
3-3 EXTREMELY EASY MAINTENANCE
Extreme ease of maintenance is realized by:
- High Parts Commonality
simplifies maintenance & lowers repair cost due to fewer parts for service.
More than 90% of component parts are in common between more than two models, in such as Muffler,
Intake and Exhaust Valves, Valve Springs, etc.
Furthermore, more than 50% of component parts are in common among EX13, EX17 and EX21, in
such as Chain Guide, Air Cleaner, Ignition Coil, etc.
- Only with ordinary tools, routine maintenance, assembly and disassembly can be performed.
3-4 EXTREMELY ADVANCED TECHNOLOGY
Extreme reliability and durability are achieved by:
- Heavy Duty Chain Driven OHC System
Oval type case-hardened steel links enhance performance and resist stretching, which result in extended
maintenance free operation.
- Completely New Main Bearing Cover’s Design
Flush-mounted main bearing cover with lower moment of deformation significantly increases reliability and
engine life.
- Superior Cooling and Lubrication System
Heat reduction is achieved by more efficient, larger and more numerous cooling fins on crankcase, cylinder
and mounting base, as well as by outstanding oil delivery system.
- Large Ball Bearings on both ends of crankshaft for maximum stability under demanding loads.
- Cast Iron Cylinder Liner resists wear
3-5 EXTREME POWER AND PERFORMANCE
Extremely Higher Power and Lower Fuel Consumption are realized by:
- High speed and homogeneous combustion achieved by sophisticated Pentroof Combustion Chamber which
includes Intake and Exhaust Valves located at optimum angle.
- Straight Intake Port with minimal air flow resistance.
Environmentally friendly
EX engines comply with EPA Phase 2 and CARB Tier II Emission Regulations in the USA.
Extreme application compatibility
With four versatile models, existing slant-cylinder engines can be easily replaced.
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4. GENERAL DESCRIPTION OF ENGINE COMPONENTS
4-1 CYLINDER AND CRANKCASE
The cylinder and crankcase are aluminum die-casting
as a single piece. A special cast iron cylinder liner is
molded into the aluminum die-casting.
The crankcase has a mounting surface on the output
shaft side to which the main bearing cover is attached.
The cylinder is inclined to the right at an angle of 25
degrees from the horizontal as viewed from the output
shaft side.
Fig. 4-1
4-2 MAIN BEARING COVER
The main bearing cover is an aluminum die-casting,
which is mounted on the output shaft side of the
crankcase. By removing the main bearing cover, the
inside of the engine can be inspected with ease. Pilots
and bosses are machined into the cover to facilitate the
direct coupling of the engine with machines such as
generators and pumps. There is an oil filling port, with
oil gauge, on either side of the cover.
Fig. 4-2
4-3 CRANKSHAFT
The crankshaft is made of spheroidal graphite cast iron,
and the crank pin is high-frequency induction-hardened.
The crank sprocket used to drive the chain and the
gear used to drive the governor gear are pressed into
the output end of the shaft.
Fig. 4-3
4-4 CONNECTING ROD AND PISTON
The connecting rod is a specially heat-treated aluminum
alloy die-casting. Its large and small ends function as
bearings. A splasher built into the connecting rod
lubricates by splashing engine oil. The piston is an
aluminum alloy casting with grooves for mounting two
compression rings and one oil ring.
Fig. 4-4
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4-5 PISTON RINGS
The piston rings are made of special cast iron. The profile of the top ring is a barrel face or tapered face, and
that of the second ring is a tapered face. There are 2 types of oil ring depending on the engine specification.
As those are interchangeable, the cutter ring with coil expander type can be selected as the spare part.
BARREL
1
2
3
(EX13/27)
TOP
RING
1
2
3
TAPER
(EX17/21)
SECOND
RING
TAPER
CUTTER RING
WITH COIL
EXPANDER
OIL
RING
THREE-PIECE
CONSTRUCTION
Fig. 4-5
4-6 CAMSHAFT
The camshaft and the sprocket are made of special
sintered alloy.They are constructed as a single piece.
The camshaft is provided with intake and exhaust cam,
and the decompression release lever is mounted on
the sprocket shaft end side.
Fig. 4-6
4-7 VALVE ARRANGEMENT
EXHAUST VALVE
INTAKE VALVE
This engine has a chain-driven overhead cam and
overhead valve construction, with a single cam
performing both intake and exhaust operations.
Fig. 4-7
4-8 CYLINDER HEAD
The cylinder head is an aluminum die-casting with a
pent roof combustion chamber construction.The intake
and exhaust ports are arranged in a cross direction to
improve combustion efficiency.
Fig. 4-8
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4-9 GOVERNOR SYSTEM
GOVERNOR GEAR
This engine is equipped with a centrifugal flyweight type
governor that makes it possible to operate the engine
at a constant speed, even with load variations. (The
governor flyweights are mounted on a governor gear.)
Fig. 4-9
4-10 COOLING SYSTEM
The engine uses a forced air-cooling system in which a cooling fan (which also works as a flywheel) forces
cooling air into the cylinder and the cylinder head. Baffles are provided to guide the flow of the cooling air.
(Model EX21 is provided with a synthetic resin cooling fan that is separate from the flywheel.)
4-11 LUBRICATION SYSTEM
The rotating parts, sliding parts and valves of the engine
are lubricated with oil in the crankcase.The oil is splashed
onto the parts by the oil splasher on the connecting rod.
4-12 TIMING CHAIN
TIMING CHAIN
Timing chain system is adopted and designed f or
lubricating for the upper portion of cylinder head.
The timing chain is engaged between the sprocket
OIL SPLASHER
portion of integrated camshaft in the cylinder head and
the crankshaft gear sprocket.
The sprocket teeth in particular shape are adopted to
enhance the durability and to realize low noise level.
Fig. 4-10
4-13 IGNITION SYSTEM
The ignition system is a transistor controlled magneto
system with the ignition timing set at 23 degrees (EX13/
17/21)[27 degrees (EX27)] before the top dead center.
The magneto consists of a flywheel and ignition coil.
The flywheel (which also works as a fan) is directly
mounted on the crankshaft and the ignition coil is
directly mounted on the crankcase.
Model EX13,17,21 and 27D has a smooth advanced
ignition timing system to improve starting performance.
IGNITION COIL
(For further details, refer to page 48, section
“7. MAGNETO”.)
FLYWHEEL
Fig. 4-11
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4-14 CARBURETOR
The engine is equipped with a hor izontal draft
carburetor. The carburetor setting is calibrated after
careful testing for optimum all-round performance
(including starting, acceleration, fuel consumption,
output power characteristics). Special attention is also
paid to the general-purpose use of the engine. (For
further information, refer to page 57, section “11.
CARBURETOR”.)
Fig.4-12
Dual Element Type
STD Type
4-15 AIR CLEANER
CLEANER
COVER
The engine uses an air cleaner that is quieter than
conventional ones. A semi-wet urethane foam element
is used in the STD air cleaner. Dual element air cleaner
(with a primary element of d ry type sponge and
secondary element of dry type paper) and other types
are also provided as special options.
CLEANER
COVER
URETHANE
FOAM
PAPER
ELEMENT
URETHANE
FOAM
Fig.4-13
4-16 BALANCER
(PROVIDED ONLY IN MODEL EX27D)
Unbalanced inertia force is cancelled by the balancer
which rotates at the same speed as the crankshaft to
effectively reduce vibration.
Fig.4-14
RETURN SPRING
ROCKER ARM
4-17 DECOMPRESSION SYSTEM
(EXHAUST VALVE SIDE)
The automatic decompression system is mounted on
the camshaft. It opens the exhaust valve before the
compression top, thereby alleviating the compression
pressure and reducing the force required to pull the
recoil starter.
During engine operation, the decompression system is
overpowered by centrifugal force and compression is
fully utilized to produce power.
EXHAUST
VALVE
CAMSHAFT
Fig.4-15
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4-18 SECTIONAL VIEW OF THE ENGINE
Cross sectional view – across the shaft
TANK CAP
FUEL TANK
GOVERNOR SHAFT
BLOWER HOUSING
GOVERNOR LEVER
GOVERNOR GEAR
CRANKSHAFT
CONNECTING ROD
STARTING PULLEY
RECOIL STARTER
FLYWHEEL
CHARGE COIL
(OPTION)
OIL SENSOR
(OPTION)
MAIN BEARING COVER
Fig. 4-16
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Cross sectional view – along the shaft
FUEL STRAINER
PISTON
MUFFLER COVER
MUFFLER
GOVERNOR LEVER
FUEL TANK
CHAIN GUIDE
EXHAUST
VALVE
TAIL SCREEN
or DEFLECTOR
(OPTION)
SPARK
ARRESTER
(OPTION)
GOVERNOR
GEAR
MAGNETIC
SWITCH
ROCKER
ARM
CAMSHAFT
INTAKE VALVE
PISTON PIN
TIMING
CHAIN
PISTON RING
STARTING
MOTOR
(OPTION)
TENSIONER
OIL GAUGE
FILLER PLUG
CONNECTING ROD
OIL DRAIN PLUG
OIL SENSOR
(OPTION)
CRANKCASE
CRANKSHAFT
Fig. 4-17
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5. DISASSEMBLY AND REASSEMBLY
5-1 PREPARATIONS AND PRECAUTIONS
(1) When disassembling the engine, memorize the location of each part so that you can reassemble the engine
correctly. If necessary, attach identification tags with the required assembly information to the parts.
(2) Store groups of parts in separate boxes.This will make reassembly easier.
(3) To prevent parts from being mislaid, keep each group provisionally assembled after removing the parts from
the engine.
(4) Handle the disassembled parts with the utmost care. Clean them with cleaning oil if necessary.
(5) Use the correct tools in the correct way when disassembling and reassembling the engine.
5-2 SPECIAL TOOLS
Tool name
Use
Flywheel puller
For pulling off the flywheel
Commercially available product
FLYWHEEL PULLER
Fig. 5-1
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5-3 DISASSEMBLY PROCEDURE
Step
Parts to remove
Remarks and procedures
Fasteners
14 mm spanner
1
Drain the engine oill
(1) Remove a drain plug (M14×12mm)
located on both sides of the case.
Take care not to lose the gaskets.
(2) To discharge oil quickly, remove the oil
guage.
OIL GAUGE
GASKET
STEP 1
GASKET
DRAIN PLUG
Fig. 5-2
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Step
Parts to remove
Remarks and procedures
Remove the air cleaner cover.
Fasteners
Air cleaner cover
2
Air cleaner
Remove the element, and remove the air
cleaner while pulling the breather pipe away
from the rocker cover.
10 mm box spanner
M6 nut: 2 pcs.
M6 × 20 : 1 pc.
3
STD TYPE
DUAL ELEMENT TYPE
STEP 3
STEP 3
AIR CLEANER COVER
AIR CLEANER
COVER
URETHAN FOAM
PAPER
ELEMENT
URETHANE FOAM
M6 x 20
FLANGE BOLT : 1 pc.
AIR CLEANER COVER
STEP 2
M6 FLANGE
NUT : 2 pcs.
BREATHER
PIPE
Fig. 5-3
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Step
Parts to remove
Stop switch
Remarks and procedures
Fasteners
Disconnect the wire and remove the stop
switch from the blower housing.
4
Recoil starter
Remove the recoil starter from the blower
housing.
10 mm box spanner
M6 × 8mm : 4 pcs.
5
6
Blower housing
Baffle 2 (head)
Baffle 3
(1)Remove the blower housing from the
crankcase.
(2)Remove the baffle 2 (head) and baffle 3.
10 mm box spanner
M6 × 12mm : 4 pcs.
10 mm box spanner or
spanner
M6 × 12mm : 2 pcs.
(Baffle 2 (head))
M5 tapping bolt : 2 pcs.
(Baffle 3)
M6 x 8 BOLT : 4 pcs.
M6 x 12 BOLT : 4 pcs.
STEP 4
STEP 5
M4 TAPPING SCREW : 2 pcs.
STOP SWITCH
RECOIL STARTER
BLOWER HOUSING
STEP 6
BAFFLE 2 (HEAD)
BAFFLE 3
(EX21 ONLY)
M6 x 12 BOLT : 1 pc.
M5 TAPPING BOLT : 2 pcs.
STEP 6
Fig. 5-4
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Step
Parts to remove
Fuel tank
Remarks and procedures
Fasteners
(1) Drain fuel from the carburetor drain.
(2) Remove the fuel tank mounting nuts
and bolts from the crankcase.
10 (12) mm spanner or box
wrench
M6 nut : 2 pcs.
(3) Disconnect the fuel pipe from the carburetor.
(See Fig. 5-6)
(4) Remove the fuel tank from the crankcase.
(Models EX13, 17 and 21)
M8 nut : 2 pcs. (Model EX 27)
M6 × 25mm : 1 pc.
(Models EX 13, 17 and 21)
M8 × 25mm : 2 pcs.
(Model EX27)
7
Muffler and Muffler cover (1) Remove the muffler cover from the
muffler.
12mm box spanner
10mm box spanner or
spanner
M6 tapping bolt : 2 pcs.
M6 × 8mm : 1 pc.
M8 nut : 2 pcs.
(2) Remove the muffler from the cylinder
head. Take care not to lose the gasket.
Take care not to cut your hand with the
muffler gasket.
8
Seal the exhaust port with adhesive
tape or plug it with cloth to prevent nuts
and other objects from falling inside.
M8 × 12mm : 1 pc.
M6 x 10
TAPPING BOLT : 2 pcs.
FUEL TANK
STEP 7
STEP 8
M6 x 8
FLANGE BOLT : 1 pc.
M8 NUT : 2 pcs.
M6 x 25 BOLT : 1 pc.
(EX13, 17, 21)
M8 x 25 BOLT : 2 pcs.
(EX27)
M6 NUT : 2 pcs.
(EX13,17,21)
M8 NUT : 2 pcs.
(EX27)
A
MUFFLER
M8 x 12
BOLT : 1 pc.
A
FUEL PIPE
GASKET
(It has two faces)
FUEL DRAIN
Seal the exhaust port with
adhesive tape or plug it with cloth.
Fig.5-5
Fig.5-6
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Step
Parts to remove
Fasteners
Remarks and procedures
Governor system
(1) Loosen the bolt and remove the governor
lever from the governor shaft. There is no
need to remove the bolt.
10 mm box spanner or
spanner
M6 × 30mm : 1 pc.
9
(2) Remove the governor spring.
(3) Remove the governor rod and the rod
spring from the carburetor.
Carburetor, Insulator
Remove the carburetor from the cylinder head.
Remove the insulator.
10
11
Speed control lever and Remove the speed control lever and bracket
Bracket from the cylinder head.
10 mm box spanner
M6 × 12mm : 2 pcs.
GOVERNOR ROD
and ROD SPRING
STEP 9
GOVERNOR SPRING
GOVERNOR LEVER
M6 x 12 BOLT : 2 pcs.
STEP 11
GOVERNOR SHAFT
SPEED CONTROL LEVER
and BRACKET
GASKET
GASKET
CARBURETOR
INSULATOR
STEP 10
Fig.5-7
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Step Parts to remove
Remarks and procedues
Fasteners
Ignition coil
12
Remove the spark plug cap from the spark plug and
remove the ignition coil from the crankcase.
10 mm box spanner
M6 × 25mm : 2 pcs.
Starting pulley
Remove the starting pulley from the flywheel.
19 (24) mm box spanner or
Fit a box wrench or a socket wrench on the flywheel nut socket wrench M14 nut
and loosen the nut by knocking the wrench sharply with a (Models EX13, 17 and 21)
hammer. (See Fig. 5-10)
M18 nut (Model EX27)
NOTE:
1) Do not insert a screwdriver or other object between the
flywheel blades, otherwise the risk of damaging the
blades might be occured.
13
2) Knock the wrench with a hammer in a counter
clockwise direction.
3) The fan of the Model EX21 engine is made of
synthetic resin. Take the utmost care when handling it.
Flywheel
14
Remove the flywheel from the crankshaft. Leave the nut
temporarily to prevent the flywheel from dropping out. Fit
the flywheel puller as shown in Figure 5-11 and remove
the flywheel from the crankshaft by rotating the bolt at the
center in a clockwise direction.
Flywheel puller
(Knock the center bolt with a hammer sometimes)
ATTACH NUT
TEMPORARILY
FLYWHEEL PULLER
Fig. 5-10
Fig. 5-11
M14 NUT : 1 pc. (EX13,17,21)
M18 NUT : 1 pc. (EX27)
STARTING
PULLEY
STEP 14
FLYWHEEL
STEP 13
M6 x 25 BOLT and
WASHER : 2 pcs.
STEP 12
GROMMET
(EX13,17,21 only)
Fig. 5-9
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20
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Step
Parts to remove
Remarks and procedures
Fasteners
Electric starter (option) (1) Disconnect the grounding cable from battery.
Control box,
Diode rectifier,
Magnetic switch
(2) Disconnect the wire leading from the key
switch ST terminal to the magnetic switch. 12 mm box spanner
15
(3) Disconnect the wire that connects the
positive terminal of the battery to the
magnetic switch.
M8 nuts
10 mm box spanner
12 mm box spanner
(4) Remove the electric starter.
M6 NUT : 1 pc. (EX17,21)
M8 NUT : 1 pc. (EX27)
ELECTRIC STARTER
(option)
EX27
M8 x 28 BOLT : 2 pcs.
EX17, 21
UPPER SIDE
STEP 15
M6 x 30 FLANGE BOLT : 1 pc.
DOWN SIDE
M6 x 20 FLANGE BOLT : 1 pc.
Fig. 5-8
-
21
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Step
Parts to remove
Baffle 1 (case)
Remarks and procedures
Remove the baffle 1 (case)
Fasteners
M6 × 12mm : 1 pc.
(Models EX13, 17 and 21)
M8 × 12mm : 1 pc.
(Model EX27)
16
Charge coil (option)
Spark plug
Remove the charge coil.
(For EX27, remove the wire clamp together)
box spanner
M6 × 20mm : 2 pcs.
+ screwdriver
17
18
Remove the spark plug from the cylinder head. 21 mm plug wrench
M6 x 12 FLANGE BOLT : 1 pc. (EX13, 17, 21)
M8 x 12 FLANGE BOLT : 1 pc. (EX27)
For the model without electric starter.
BAFFLE 1 (CASE)
STEP 16
A
STEP 17
CHARGE COIL
SPACER
BOLT
SPACER
EX13 15W
40W
M6 x 40L
M6 x 35L
M6 x 35L
M6 x 40L
M6 x 25L
M6 x 35L
M6 x 40L
M6 x 25L
M6 x 20L
M6 x 30L
M6 x 25L
EX17 15W
40W
STEP 18
200W
NA
EX21 15W
40W
200W
NA
NA
NA
NA
SPARK PLUG
EX27 15W
40W
200W
CLAMP
CHARGE COIL
VIEW (EX27 only)
A
Fig.5-12
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22
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Step
Parts to remove
Rocker cover
Remarks and procedures
Fasteners
(1) Remove the rocker cover from the
cylinder head.
(2) Remove the gasket (rocker cover).
10 mm box spanner
M6 × 12mm : 4 pcs.
19
Rocker arm
Remove the pin (rocker arm) and the rocker
arm from the cylinder head at the compression
top dead center. (See Fig. 5-14b)
20
ROCKER ARM
(EXHAUST VALVE SIDE)
PIN
The position of compression top dead center
Punch marks
(ROCKER ARM)
ROCKER ARM (INTAKE VALVE SIDE)
Fig. 5-14a
Fig. 5-14b
ROCKER ARM
(EXHAUST
STEP 20
VALVE SIDE)
PIN
(ROCKER ARM)
ROCKER ARM
(INTAKE VALVE SIDE)
CLOSE-UP A
GASKET (ROCKER COVER)
A
STEP 19
ROCKER COVER
M6 x 12 BOLT : 4 pcs.
Fig. 5-13
-
23
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Step
Parts to remove
Remarks and procedures
Fasteners
Main bearing cover
(1) Remove the flange bolts of main bearing
cover from the crankcase.
12 mm box spanner
M8 × 35mm : 6 pcs.
(Models EX13, 17 and 21)
M8 × 35mm : 7 pcs.
(Model EX27)
Remove the main bearing cover while
tapping gently around the cover using
a plastic hammer or similar tool.
(See Fig. 5-16)
21
Be careful not to damage the oil gauge
or oil seal or not to lose the pipe knocks.
Fig. 5-16
M8 x 35mm : 6 pcs.
(MODELS EX13,
17 AND 21)
M8 x 35mm : 7 pcs.
(MODEL EX27)
STEP 21
PIPE KNOCK
MAIN BEARING COVER
Fig. 5-15
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24
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Step
Parts to remove
Remarks and procedures
Fasteners
Tensioner, Camshaft
(1) Remove the tensioner. (See Fig. 5-18a)
Do not lose the pin (tensioner).
M10 box spanner or spanner
M6 × 12mm : 1 pc.
(2) Remove the retaining bolt of pin (camshaft)
from the cylinder head. (See Fig. 5-18b)
(3) Remove the pin (camshaft), taking care not
to scratch the O-ring.
22
(4) Remove the chain from the camshaft
sprocket and then take out the camshaft.
(See Fig. 5-19)
(5) Remove the chain from the crankshaft.
PIN (CAMSHAFT)
M6 x 12 BOLT : 1 pc.
Bolt used to prevent the
pin (camshaft) from coming out
PIN (TENSIONER)
Fig.5-18a
Fig.5-18b
CHAIN
CAMSHAFT
Fig.5-19
CHAIN
CAMSHAFT
STEP 22
CHAIN
SPRING
(TENSIONER)
M6 x 12 BOLT : 1 pc.
Bolt used to prevent the
PIN (CAMSHAFT)
pin (camshaft) from coming out
TENSIONER
PIN (TENSIONER)
STEP 22
Fig. 5-17
-
25
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Step
Parts to remove
Cylinder head,
Remarks and procedures
Fasteners
(1) Remove the cylinder head from the
crankcase.
12 mm box spanner
M8 × 68mm : 4 pcs.
Chain guide
(2) Remove the cylinder head gasket from the M8 × 35mm : 1 pc.
cylinder head. Take care not to lose the
pipe knocks.
23
(3) Remove the chain guide from the top side
of the crankcase.
(If the chain guide is removed from the inner
side of the crankcase, it might be damaged.)
Intake and exhaust
valves
(1) Remove the collet valve from the
spring retainer. (See Fig. 5-21)
(2) Remove the intake valve and the exhaust
valve.
24
Fig.5-21
COLLET VALVE
SPRING RETAINER
VALVE SPRING
PIPE KNOCK
STEP 23
GASKET
INTAKE
VALVE
Push
M8 x 68 BOLT : 4 pcs.
VALVE SPRING
EXHAUST
VALVE
STEP 24
COLLET VALVE
STEM SEAL
CHAINGUIDE
CYLINDER HEAD
SPRING RETAINER
M8 x 35 BOLT : 1 pc.
(This bolt is same as the
main bearing cover bolt).
Fig.5-20
-
26
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Step
Parts to remove
Remarks and procedures
Fasteners
Connecting rod and
piston
(1) Scrape off any carbon from the cylinder
and the piston head, then remove the
connecting rod bolt.
(2) Remove the connecting rod cap.
(3) Rotate the crankshaft until the piston
comes to its top position. Push the
connecting rod and remove the piston
from the upper part of the cylinder.
10 mm box spanner
M6 × 33mm : 2 pcs.
(Models EX13, 17 and 21)
M7 × 40mm : 2 pcs.
(Model EX27)
25
Piston and piston rings (1) Remove the piston clips (2 pcs.). Take
out the piston pin and then remove the
piston from the connecting rod small end,
taking care not to damage the connecting rod
small end.
26
(2) Remove the piston rings from the piston
by spreading them at the gap.
Take special care not to damage the rings
when doing this.
STEP 26
PISTON RING
CLIP
STEP 25
CONNECTING ROD CAP
CONNECTING ROD
PISTON
PISTON PIN
CLIP
M6 x 33 (EX13, 17, 21)
M7 x 40 (EX27)
CONNECTING ROD BOLT : 2 pcs.
Fig.5-22
-
27
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Step
Parts to remove
Crankshaft
Remarks and procedures
Fasteners
(1) Remove the woodruff key (for the flywheel
magneto).
(2) Remove the crankshaft from the crankcase
27
by tapping its magneto side end with a plastic Plastic hammer
hammer, taking care not to damage the oil
seal.(See Fig.5-24)
Oil sensor (option)
(1) Remove the clamp. (See Fig. 5-25)
(2) Remove the oil sensor from the crankcase.
M6 × 12mm : 1 pc.
M6 × 16mm : 2 pcs.
28
CLAMP
OIL SENSOR
Fig.5-24
Fig.5-25
M6 x 10 TAPPING
BOLT : 1 pc. (EX27 only)
CLAMP
SHIELD PLATE
(For charge coil only)
CRANKCASE
M6 x 16
BOLT : 2 pcs.
WOODRUFF KEY
OIL
SENSOR
STEP 28
STEP 27
CRANKSHAFT
Fig.5-23
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28
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5-4 REASSEMBLY PROCEDURE
5-4-1 NOTES ON REASSEMBLY
(1) Clean the each parts carefully, taking special care with the piston, cylinder, crankshaft, connecting rod and
bearings.
(2) Scrape off any carbon deposits on the cylinder head and the piston head. Be particularly careful when
removing carbon from the piston ring grooves.
(3) Inspect the oil seals for any damage to the lip.Replace them if damaged.Apply oil to the lip beof re reassembly.
(4) Replace all the gaskets with new ones.
(5) Replace the keys, pins, bolts and nuts with new ones, if necessary.
(6) Tighten nuts and bolts to the specified torque settings.
(7) When reassembling the engine, apply oil to all moving parts.
(8) Check clearances and end plays and adjust, if necessary.
(9) When mounting any major part during reassembly of the engine, rotate it with your hand to check for any
jamming or abnormal noise.
5-4-2 ASSEMBLY STEPS AND PRECAUTIONS
(1) OIL SENSOR
(a) Mount the oil sensor and fix the wire with the clamp.
(b) Mount the shield plate only for charge coil type.
Tightening torque
10.0 N m
OIL SENSOR
(
100 kgf cm)
(7.2 ft lb.)
M6 x 16
BOLT : 2pcs.
(c) Mount the control unit. Fix the earth wire of the
control unit at the same time.
CLAMP
SHIELD PLATE(OS)
M6 x 12 BOLT : 1pc.
(See Fig. 5-49a on page 38).
Fig.5-29
(2) CRANKSHAFT
CRANKSHAFT
(a) Wrap the key-way portion of the crankshaft with
polyvinyl tape and insert the crankshaft into the
crankcase, taking care not to damage the oil seal lip.
(b) Insert the woodruff key (for the flywheel magneto).
NOTE: Do not insert the woodruff key before inserting
the crankshaft into the crankcase.
POLYVINYL TAPE
Fig.5-30
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29
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(3) PISTON AND PISTON RINGS
OPEN ENDS OF PISTON RING
Install each piston ring in the correct groove of
the piston by widening it enough to slide it over
the piston.
NOTE: Be careful not to twist the rings too much,
as they may be damaged. Install the oil
ring first, followed by the second ring and
then the top ring.
When installing the second ring, make
sure that the ‘N’ mark is face up.
(See Fig. 5-33)
Fig.5-31
BARREL
1
2
3
(EX13/27)
TOP
RING
1
2
3
TAPER
(EX17/21)
SECOND
RING
TAPER
CUTTER RING
WITH COIL
EXPANDER
OIL
RING
THREE-PIECE
CONSTRUCTION
Fig.5-32
MARK "R"
MARK "N"
EX13
EX17, EX21, EX27
Fig.5-33
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(4) PISTON AND CONNECTING ROD
The piston is attached to the connecting rod b y
the piston pin.
When assembling the piston and connecting rod,
make sure to align the mark on the piston head with
the ‘MAG’ mark on the connecting rod.
When assembling the
piston and connecting
rod, make sure to align
the mark on the piston
head with the ‘MAG’ mark
on the connecting rod.
NOTE 1: Before assembling the connecting rod,
apply oil to its small end.
NOTE 2: Be sure to insert the clips in the two ends
of the piston pin and check the clips for
any play.
Fig. 5-34
(5) CONNECTING ROD
PISTON RING GUIDE
CONNECTING ROD
(a) Install the piston and connecting rod assembly into
the cylinder by holding the piston rings with the
ring guide, with the ‘MAG’ mark on the connecting
rod on the flywheel side. (If you do not have a ring
guide, hold the piston rings with the fingers and
tap the upper part of the piston with a piece of
wood.)
NOTE 1: Apply oil to the piston rings, the large end
of the connecting rod and cylinder before
installing the connecting rod into the
cylinder.
"MAG" MARK
FLYWHEEL SIDE
NOTE 2: The piston ring gaps should be positioned
around the piston at 90-degree intervals.
(See Fig. 5-36)
Fig.5-35
SECOND RING
OIL RING
TOP RING
Fig.5-36
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31
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(b) Rotate the crankshaft down to the bottom dead center
and lightly tap the piston head until the large end of
the connecting rod touches the crank pin.
(c) To mount the connecting rod, line up the matching
marks and fit the clinch portions firmly together.
ALIGNMENT
MARKS
Tightening torque
ALIGNMENT
MARKS
EX13,17,21
0 - 15.0 N m
(130 - 150 kgf cm)
(9.4 - 10.8 ft lb.)
EX27
13.
17.0 - 20.0 N m
(170 - 200 kgf cm)
(
12.3 - 1
4.
5
ft lb.)
(d) Check for free movement of the connecting rod by
turning the crankshaft slowly.
Fig. 5-37
(6) INTAKE AND EXHAUST VALVES
Take the following points into account when
mounting the intake and exhaust valves on the
cylinder head.
NOTE 1: Replace the valve with a new one if it shows
signs of wear. (Refer to the “STANDARD
REPAIR TABLES” on page 78 and 79.)
NOTE 2: Carefully scrape off any carbon deposits
on the combustion chamber. Apply oil to
the valve stems before mounting the intake
and exhaust valves. Insert the valves in the
cylinder head and place it on a le vel
workbench. Next, mount the valve springs,
the spring retainers and collet v alves.
(Mount the stem seal on the intake valve
guide.)
Fig. 5-38a
COLLET VALVE
SPRING RETAINER
VALVE SPRING
CYLINDER HEAD
INTAKE VALVE
STEM SEAL
EXHAUST VALVE
COLLET VALVE
VALVE SPRING
SPRING RETAINER
Fig.5-38b
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32
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(7) CHAIN GUIDE
CHAIN GUIDE
Mount the chain guide to the crankcase.
Model EX21
mounting position
Models EX13, 17 and
27 mounting positions
Fig. 5-39b
Fig. 5-39a
(8) CYLINDER HEAD
Inspect and repair any scratches on mounting surface and replace head gasket to new one before installing.
Tightening Torque
1st step
2nd step
1
1
Cylinder head bolts
Remarks
4
4
5
3
3
2
2
25.0 - 27.0 N m
(250 - 270 kgf cm)
(18.1 -19.5 ft lb.)
Re-use
M8 × 68mm
17.0 - 19.0 N m
(170 - 190 kgf cm)
(12.3 - 13.7 ft lb.)
flange bolt : 4 pcs.
28.0 - 30.0 N m
(280 - 300 kgf cm)
(20.3 - 21.7 ft lb.)
When replace to new cylinder
head and flange bolts
M8 × 35mm
flange bolt : 1 pc.
--------
--------
Tighten the cylinder head bolts in diagonal order.
(1) Re-use (Oil the screw thread)
Tighten all bolts (5pcs) by 18 ± 1 N m primary,
and then tighten longer ones (M8× 68mm flange
bolt: 4pcs) by 26 ± 1 N m.
PIPE KNOCK
GASKET
M8 x 68 BOLT : 4 pcs.
(2) When replace to new cylinder head and flange
bolts (Oil the screw thread)
Tighten all bolts (5pcs) by 18 ± 1 N m primary,
and then tighten longer ones (M8× 68mm flange
bolt: 4pcs) by 29 ± 1 N m.
PIPE
KNOCK
CYLINDER HEAD
M8 x 35 BOLT : 1 pc.
Fig. 5-40
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33
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(9) SETTINGTHE TIMINGCHAIN
(a) Align the timing mark on the crankshaft sprocket with the mark plate of the timing chain.
(b) Align the timing mark on the crankshaft sprocket with the mark plate of the opposite end of the timing chain.
Model
EX13
EX17
EX21
EX27
Number of oval steel link
86
88
92
100
CHAIN GUIDE FITTING POSITION
MARK PLATE
Model EX13
The mark plate does
not have a camshaft
side or crankshaft
sprocket side.
The position of
top dead center
TIMING MARK
ROLL PIN
TIMING MARK
CAMSHAFT SPROCKET
CRANKSHAFT SPROCKET
MARK PLATE
CHAIN GUIDE FITTING POSITION
MARK PLATE
Model EX17, 27
The mark plate does
not have a camshaft
side or crankshaft
sprocket side.
TIMING MARK
ROLL PIN
TIMING MARK
CAMSHAFT SPROCKET
CRANKSHAFT SPROCKET
MARK PLATE
MARK PLATE
CHAIN GUIDE FITTING POSITION
Model EX21
The mark plate does
not have a camshaft
side or crankshaft
sprocket side.
TIMING MARK
ROLL PIN
TIMING MARK
CAMSHAFT SPROCKET
CRANKSHAFT SPROCKET
MARK PLATE
Fig. 5-41a
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(10) MOUNTINGTHE CAMSHAFT ONTHE CYLINDER HEAD
Mount the camshaft on the cylinder head by inserting the pin (camshaft) through the head.
Fix the bolt to prevent the pin (camshaft) from coming out.
PIN (CAMSHAFT)
CHAIN
M6 x 12 BOLT : 1 pc.
Bolt used to prevent the
pin (camshaft) from coming out
CAMSHAFT
CHAIN
CAMSHAFT
CHAIN
SPRING
(TENSIONER)
M6 x 12 BOLT : 1 pc.
Bolt used to prevent the
PIN(CAMSHAFT)
pin (camshaft) from coming out
TENSIONER
PIN(TENSIONER)
Fig. 5-41b
(11) MOUNTING THE TENSIONER
PIN
(TENSIONER)
SPRING
(TENSIONER)
PIN (TENSIONER)
TENSIONER
Fig. 5-42a
Fig. 5-42b
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35
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(12) BALANCER SHAFT (OPTION)
(for EX27 only)
TIMING MARK
BALANCER GEAR
Mount the balancer shaft on the crankcase, align
the timing marks on the balancer gear and the
crankshaft gear.
NOTE: Incorrect alignment of the timing marks
can result in malfunction of the engine,
leading to damage due to interference of
the parts.
CRANKSHAFT GEAR
Fig. 5-43
(13) MAIN BEARING COVER
Apply oil to the bearing and the oil seal lip when mounting the main bearing cover. Also apply sealant
(Three Bond ì1215î) to the surface of the crankcase.To avoid damaging the oil seal lip, wrap the crankshaft
key-way portion with polyvinyl tape before mounting the main bearing cover.
NOTE: Be careful that the lever portion of governor shaft does not face the main bearing cover.
Tightening torque
22.0 - 24.0 N m
(220 - 240 kgf cm)
(16.2 - 17.7 ft lb.)
GOVERNOR SHAFT
CRANKSHAFT
M8 x 35 BOLT : 6 pcs.
(EX13, 17, 21)
M8 x 35 BOLT : 7 pcs.
(EX27)
SEALANT
(
)
Three bond "1215"
MAIN BEARING COVER
Fig. 5-44
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36
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(14) Pass the pin (rocker arm) through the rocker arm
ROCKER ARM
(EXHAUST VALVE SIDE)
PIN
and mount them on the cylinder head.
(ROCKER ARM)
NOTE 1: Conduct this job at the compression top
dead center.
(The position of two punch marks on cam
sprocket is in parallel with the cylinder
head surface at a time.)
Punch
marks
The position of compression
top dead center
ROCKER ARM
(INTAKE VALVE SIDE)
NOTE 2: Make sure that the piston is at the
compression top dead center by checking
mutual position between the flywheel and
the ignition coil or by checking that the
key way is at the top.
Fig. 5-45
EX13, 17, 21
(See each Fig.5-46)
The position of
top dead center
(15) VALVE CLEARANCE ADJUSTMENT
EX27
Temporarily fit the flywheel.
Rotate the crankshaft up to the compression top
dead center and inser t the thickness gauge
between the valve and the adjusting screw of
rocker arm to measure the clearance.
The position of
top dead center
[Adjustment method]
Loosen the nut on the adjustment screw and turn
the screw to adjust the valve clearance. When
the valve clearance is correct, tighten the nut.
The key way
is at the top
Valve clearance (when the engine is cold)
Fig. 5-46
0.12 +0.03 mm
Intake valve side
0
THICKNESS GAUGE
NUT
(0.0047 +0.0012 in.)
0
Exhaust valve side
ADJUSTMENT
SCREW
ROCKER ARM
(EXHAUST
VALVE SIDE)
5.0 - 7.0 N m
Tightening
(50 - 70 kgf cm)
torque
(3.6 - 5.1 ft lb.)
NOTE: After adjusting the valve clearances, rotate
the crankshaft and check again that the
intake and exhaust valve clearance are
correct.
ROCKER ARM
(INTAKE VALVE SIDE)
Fig. 5-47
-
37
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(16) ROCKER COVER
SPARK PLUG
Replace the gasket with a new one, and mount
the rocker cover.
M6 ✕ 12mm flange bolt :4 pcs.
Tightening torque
5.0
50
(3.6 - 5.1 ft lb.)
-
7.0 N m
70 kgf cm)
(
-
GASKET
(ROCKER COVER)
(17) SPARK PLUG
ROCKER
COVER
M6 x 12
BOLT : 4 pcs.
Remove any carbon deposits from the spark plug
and inspect the electrode for damage before
mounting. Replace with a new one, if necessary.
Fig. 5-48
Spark plug: NGK BR-6HS
or CHAMPION RL86C
Tightening torque
New spark plug
12 0 - 15.0 N m
(120 - 150 kgf cm)
(8.7 - 10.8 ft lb.)
Re-tightening torque
Electrode gap
0.6 mm - 0.7 mm
.
23.0 - 27.0 N m
(230 - 270 kgf cm)
(16.6 - 19.5 ft lb.)
(18) BAFFLE 1 (CASE)
Align the top and bottom of the baffle 1 (case)
with the crankcase and mount it with the bolts.
[
Model with electric starter]
[
Model without electric starter]
Mount the electric starter and the charging coil,
referring to the illustrations of disassembly.
M6 ✕ 12 mm bolt : 1 pc.
(Models EX13, 17 and 21)
Tightening torque
M8 ✕ 12 mm bolt : 1 pc. (Model EX27)
EX13, 17, 21
EX27
4.0 N m
(40 kgf cm)
(2.9 ft lb.)
12.0 N m
(120 kgf cm)
(8.7 ft lb.)
UPPER
BAFFLE 1 (CASE)
M6 x 12 FLANGE BOLT : 1 pc.
(EX13, 17, 21)
M8 x 12 FLANGE BOLT : 1 pc.
(EX27)
EX13, 17, 21
TO IGNITION COIL
LOWER
BAFFLE 1
(CASE)
OIL SENSOR
UNIT
HOOK
TO OIL SENSOR
Fig. 5-49b
Fig. 5-49a
-
38
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(19) FLYWHEEL AND STARTING PULLEY
FLYWHEEL
NOTE: When mounting the flywheel, be sure to
wipe off any oil on the tapered portion of
the crankshaft and flywheel.
Mount the flywheel on the crankshaft. (Tighten
the flywheel together with the starting pulley.)
STARTING PULLEY
Tightening torque
Align the 2 bosses of starting pulley with the depression of flywheel.
59.0
590
42.7
-
64.0 N m
640 kgf cm)
- 46.3 ft lb.)
Fig. 5-50
(
-
(
M14 nut : 1 pc. (EX13, 17, 21)
M18 nut : 1 pc. (EX27)
Fig. 5-51
THICKNESS
GAUGE
(20) IGNITION COIL
When mounting the ignition coil, inser t a
thickness gauge between the ignition coil and
the flywheel to check the air gap.
Air gap
0.3 mm - 0.5 mm
Tightening torque
IGNITION COIL
7.0 - 9.0 N m
(70 - 90 kgf cm)
(5.1 - 6.5 ft lb.)
Fig. 5-52
M6 ✕ 25 bolt and washer : 2pcs.
To STOP
SWITCH
Fig. 5-53
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(21) SPEED CONTROL LEVER, BRACKET AND BAFFLE
Mount the speed control lever and bracket, baffle 2 (head) and baffle 3 on the crankcase.
NOTE : The baffle 3 is used for Model EX21 only.
(22) CARBURETOR
(a) Replace the gasket of insulator with a new one and mount the insulator on the cylinder head intake
side.
(b) Mount the carburetor.
SPEED CONTROL LEVER
and BRACKET
M6 x 12 BOLT : 2 pcs.
CARBURATOR
INSULATOR
GASKET
GASKET
BAFFLE 2 (HEAD)
M6 x 12 BOLT
: 1 pce.
BAFFLE 3
(EX21 ONLY)
A
M5 TAPPING BOLT : 2 pcs.
Detail A
Fig. 5-54
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(23) GOVERNOR LEVER
(a) Pass the governor rod through the rod spring, then connect to the throttle lever of the carburetor.
(b) Attach the governor rod and rod spring to the governor lever, then mount the governor lever on the governor
shaft. Do not adjust the bolt on the governor lever yet.
(c) Connect the governor lever and the speed control lever with the governor spring.
NOTE : See page 42 for details on the adjustment method after mounting air cleaner base.
Variation of the governor spring
The dimensions of the governor spring are different each other according to the Hz.
The governor spring for the standard engine is same as that for the engine to be connected to the 60Hz generator.
Discrimination according to the dimensions:
EX13, 17 / 50Hz
EX21, 27 / 50Hz
10
20
15
15
Color : Gold
Color : Gold
(Governor lever side)
(Speed con. side)
EX13, 17, 21, 27 / 60Hz (STD)
26
15
Color : Silver
GOVERNOR ROD
and ROD SPRING
GOVERNOR
LEVER
GOVERNOR SPRING
Long
length side
Short
length side
SPEED CONTROL LEVER
and BRACKET
Fig. 5-55
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M6 x 20
FLANGE BOLT : 1 pc.
(24) AIR CLEANER BASE
Insert the breather pipe into the rocker cover
and then mount the air cleaner base.
AIR CLEANER BASE
M6 flange nut : 2 pcs.
M6 x 20 mm flange bolt : 1 pc.
Tightening torque
6.0
60
(4.3 - 5.8 ft lb.)
-
8.0 N m
80 kgf cm)
(
-
BREATHER
PIPE
M6 FLANGE
NUT : 2 pcs.
Fig. 5-57
Governor system adjustment method
The governor unit is a centrifugal flyweight type and is installed on the governor gear.
Since it automatically adjusts the throttle valve of the carburetor by means of a link mechanism, it is possible to
maintain a constant engine speed, even with load variations.
(1) Turn the speed control lever to the full speed position, making sure that the carburetor throttle valve is fully
open.
(2) Hold the top of the governor shaft with the plier and turning it clockwise as far as it will go.Tighten the bolt on
the governor lever.
GOVERNOR
LEVER
Tightening torque
GOVERNOR ROD
8.0
80
(5.8 - 7.2 ft lb.)
-
10.0 N m
100 kgf cm)
and ROD SPRING
(
-
GOVERNOR
SPRING
GOVERNOR
SHAFT
Fig. 5-58
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(25) MUFFLER
M6 x 10
TAPPING BOLT : 2 pcs.
(1) Mount the muffler and the gasket on the cylinder head.
GASKET
(Attention to the wrong side and right side)
MUFFLER SIDE
(RIGHT SIDE)
M6 x 8
FRANGE BOLT : 1 pc.
M8 NUT : 2 pcs.
MUFFLER
CYLINDER SIDE
(WRONG SIDE)
Take utmost care not to cut your
hand with the muffler gasket
M8 ✕12 mm bolt : 1 pc.
M8 x 12 BOLT : 1 pc.
M8 nut : 2 pcs.
Tightening torque
GASKET
(Attention to the wrong
side and right side)
18.0
180
13.0
-
22.0 N m
220 kgf cm)
- 15.9 ft lb.)
(
(
-
(2) Mount the muffler cover on the muffler.
M6 ✕ 8 mm flange bolt : 1 pc.
M6 ✕ 10 mm tapping bolt : 2 pcs.
NOTE : Be sure to remove any tape or cloth used
to cover the exhaust port when the engine
Fig. 5-59a
was disassembled
.
(26) FUELTANK
(1) Mount the fuel strainer to the fuel tank.
FUEL
STRAINER
Tightening torque for fuel strainer
FUEL PIPE
3.0
30
2.2
-
4.0 N m
40 kgf cm)
2.9 ft lb.)
(
(
-
-
HOSE
CLAMP
M6 NUT
: 2pcs.
(2) Connect the fuel pipe and fix it with a clamp.
Model
EX13
EX17
EX21
EX27
M6 x 25 BOLT : 1pc.
(EX13, 17, 25)
M8 x 25 BOLT : 2pcs.
(EX27)
Fuel pipe length
mm(in.)
145(5.7) 150(5.9) 155(6.1) 195(7.7)
NOTE : Make sure the fuel pipe is located on the boss,
as shown in the illustration, in order to prevent
Fig. 5-59b
the pipe from attaching to the flywheel
.
In case the pipe is routed improperly, the pipe might
be hit by the flywheel and will be damaged.
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(3) Mount the fuel tank on the crankcase.
M6 nut : 2 pcs.
FUEL PIPE
M6 ✕ 25 mm bolt : 1 pc. (Models EX13, 17 and 21)
M8 ✕ 25 mm bolt : 2 pcs. (Model EX27)
BOSS
Fig. 5-59c
(27) BLOWER HOUSING AND RECOIL STARTER
(1) Mount the ignition coil cord on the crankcase by aligning it with the baffle 1 (case).
(2) Mount the blower housing on the crankcase.
M6 12 mm bolt : 4 pcs.
M6 x 8 BOLT : 4 pcs.
(3) Mount the recoil starter on the blower housing.
M6 8 mm bolt : 4 pcs.
M6 x 12 BOLT : 4 pcs.
RECOIL STARTER
BLOWER HOUSING
Fig. 5-60
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(28) STOP SWITCH
STOP SWITCH
(1) Mount the stop switch on the blower housing.
(2) Refer to the wiring diagram (See page 51 and 52) for
wiring details.
Fig. 5-61
(29) AIR CLEANER
Mount the air cleaner element and cleaner cover.
Type
Dual element
STD
Fig. 5-62
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(30) EXTERNAL INSPECTION
Reassembly is completed. Check that the wiring is correct and that there are no loose nuts and bolts or any
other faults visible on the outside of the engine.
(31) FILLING WITH ENGINE OIL
Use the automobile engine oil of API service class SE or higher grade.
The amount of oil depends on the engine model.Refer to the table below.
Model
EX13
Model
EX17
Model
EX21
Model
EX27
Engine oil volume
0.6 L
1.0L
(32) BREAK-IN OPERATION
A new engine or an engine that has been completely overhauled by being fitted with a new piston, rings,
valves and connecting rod should be thoroughly RUN-IN before being put back into service.
Good bearing surfaces and running clearances between the various parts can only be established by operating
the engine under reduced speed and loads for a short period of time.
While the engine is being tested, check for oil leaks.
Make final carburetor adjustment and regulate the engine operating speed.
Model
EX13
Model
EX17
Model
EX21
Model
EX27
Engine
Speed
Step
Time
Step 1
Step 2
Step 3
Step 4
Step 5
No Load
2500 r.p.m.
3000 r.p.m.
3600 r.p.m.
3600 r.p.m.
3600 r.p.m.
10 min.
10 min.
10 min.
30 min.
30 min.
No Load
No Load
1.5 HP
3 HP
2 HP
4 HP
2.5 HP
5 HP
3.5 HP
7 HP
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6. ENGINE OIL
Using engine oil of the correct grade and viscosity greatly lengthens engine life and improves performance.
Too much or too little oil can also result in serious problems, including engine seizure.
6-1 CLASSIFICATION BY OIL GRADE
API (American Petroleum Institute)
Classification
SA
SB
SC
SD
SE
SF
SG
SH
SJ
Grades suited for Robin Engine:SE or higher (SG,SH or SJ in recomended)
6-2 CLASSIFICATION BY OIL VISCOSITY
SAE (Society of Automotive Engineers)
5W
10W
20W
Single grade
#20
#30
#40
10W
-30
Multigrade
10W
-
40
Ambient
temperature
Be sure to use automobile engine oil of the viscosity shown in the table above, depending on environmental air
temperature.
When the air temperature falls below –20 C or rises above 40 C , be sure to choose engine oil of appropriate
viscosity and grade, according to the prevailing conditions.
Care must be taken when using multi-grade engine oil, because the oil consumption rate tends to increase
when the air temperature is high.
6-3 ADDING AND CHANGING ENGINE OIL
Engine oil inspection and filling up............. Every time you use the engine
(add engine oil up to the designated maximum level)
Engine oil change ..................................... First time ............After 20 hours’ use
Thereafter ...........Every 100 hours’ use
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7. MAGNETO
7-1 MAGNETO
The Robin Engine uses a T.I.C. type breakerless magneto ignition system.
(1) T.I.C. (TRANSISTOR IGNITER CIRCUIT) has the ignition coil outside the flywheel, which is the standard
specification. A charge coil system is available as an option.
(The flywheel is a specialized piece of equipment.)
As for the lighting coil, the ignition coil is outside the flywheel and a lighting coil is inside.
7-2 INSPECTING THE MAGNETO
If the engine does not start, has difficulty starting, or does not run smoothly, check the magneto for defects
according to the following procedure:
(1) Carefully check the high-tension cable for any damage or short circuiting.
(2) Check the sparking.
Take the spark plug out of the cylinder head, connect the spark plug with the plug cap and ground it
on the cylinder head or any other metallic part of the engine.
(The gap between the electrodes of the spark plug should be between 0.6 mm and 0.7 mm).
Rotate the engine by pulling the recoil starter and check the spark plug gap for sparking. If the spark
plug is sparking, check the intensity of the spark.
(Before checking the spark plug, disconnect the primary wire from the connector.)
Next, disconnect the spark plug from the plug cap and check the end of the high-tension cable for
sparking.
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7-3 IGNITION SYSTEM (EX13 ,17, 21)
7-3-1 TYPE OF IGNITION SYSTEM
EX13, 17 and EX21 have the T.I.C. (Transister, Igniter, Circuit) pointless ignition system.
As optional parts, these ignition system may be implemented with lamp coil, charge coil and excitor coil.
I
1
LowSpeed
Ignition
I
3
Timing
Control Circuit
Automatic
Advancing
Control
I
5
I
2
Circuit
I
4
I
6
Fig. 7-1(a)
ELECTRONIC ADVANCING FLYWHEEL
MAGNETO SYSTEM
7-3-2 BASICTHEORY
(B.T.D.C)
To ensure the easy startability of the engine, the
step advancing ignition timing system is
incorporated in the ignition coil. This system
enables the engine to have basically two different
ignition timings according to the engine speed.
Following are the explanation how the system works.
23
ࠑ STEP ADVANCING
1) At lower speed of the engine
15
ࠑ Rotation of the flywheel induces current I1,
as this current flows through the base terminal
of the power transister, it is activated and the
current I2 starts flowing.
500
1000
2000
3000(r.p.m.)
ENGINE REVOLUTION
Fig. 7-1(b)
As the engine reaches the ignition timing, the ignition timing control circuit for the lower engine speed is
activated and lets the current I3 flow through the base terminal of the power transistor.
This generates the collector current I4 which will bypass the current I1 and abruptly shut off the current I2
because the power transistor is turned off.
This sudden current change generates a big voltage on the secondary side of the ignition coil and which
sparks the spark plug.
2) At the higher engine speed
Rotation of the flywheel generates the current I1 as this current flows through the base terminal of the power
transistor, it is activated and the current I2 starts of flow.
As the engine reaches the ignition timing, the ignition timing control circuit for the higher engine speed is
activated and provides the base current I5 to the power transistor.This current induces the collector current
I6
and will bypass the current I1 to shut down the current I2 abruptly because the power transistor is turned off.
This sudden current change generates a big voltage on the secondary side of the ignition coil and which will
spark the spark plug.
The ignition timing control circuit for the higher engine speed is activated, sooner than the control circuit for
the lower speed and not activated when the engine speed is in a lower range.
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7-4 IGNITION SYSTEM (EX27)
7-4-1 IGNITION COIL INTERNAL CIRCUIT
Base Resister
2
I1
I2
1
7
5
3
I3
Low Speed Ignition
Timing Control
Circuit
Advancing Control
Circuit
I4
6
I5
4
Fig.7-2a
7-4-2 IGNITION TIMING CHARACTERISTIC
LINEAR ADVANCING
35
30
25
20
15
10
5
0
0
500 1000 1500 2000 2500 3000 3500 4000
ENGINE REVOLUTION (R.P.M.)
Fig.7-2b
7-4-3 BASIC THEORY
(a) Revolution of the flywheel generates electricity on the primary side of the ignition coil (1), and the base
current I1 flows to the power transistor (2). Current I1 turns the power transistor “ON” and the electric
current I2 flows.This is the same situation when the contact breaker is closed in a case of breaker point
type ignition system.
(b) At lower engine revolution, the low speed ignition timing control circuit (3) operates to run the gate
current I3 to turn the control thyristor (5) “ON”, thus the current I1 bypass the thyristor as current I5
.
At this moment, the power transistor (2) turns “OFF” and the current I2 is shut off abruptly resulting
in the high voltage generated in the secondary coil (7) which produces sparks at the spark plug.
The ignition timing at lower engine revolution is less advanced as shown in the above chart.
(c) At higher engine revolution (over 2,000rpm), advancing control circuit (4) operates to run the gate current
I4
to turn the control thyristor (5) “ON”, thus the current I1 bypass the thyristor as current I5.
At this moment, the power transistor (2) turns “OFF” and the current I2 is shut off abruptly resulting
in the high voltage generated in the secondary coil (7) which produces sparks at the spark plug.
At over 2,000rpm, ignition timing on each engine revolution is controlled by advancing control circuit (4)
that receive electrical information from revolution sensing resister (6).
The advancing of ignition timing from lower to higher engine revolution changes lineally as shown in
the above chart.
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8. WIRING DIAGRAM
8-1 MODEL WITHOUT ELECTRIC STARTER (Models EX13, 17, 21 and 27)
Spark plug
Black
Ignition coil
(with built-in transistor)
Flywheel
Fig. 8-1
8-2 MODEL WITH ELECTRIC STARTER (Models EX17 and 21)
Spark plug
Black
Magneto
Ignition coil
Key switch
+M
-
M
Charge coil
ST
Diode rectifier
B
Red
LA106
LA406
Battery
(12V24AH)
LA306
Key switch
066-00003-30
-M +M
B
S
OFF
Magnetic switch
ON
Electric starter
START
Fig. 8-2
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8-3 MODEL WITH ELECTRIC STARTER (Model EX27)
Spark plug
Black
Magneto
Ignition coil
Key switch
+M
-M
Charge coil
ST
B
Diode rectifier
Red
LA108
LA408
Battery
(12V24AH)
Key switch
066-00003-30
-M +M
B
S
OFF
ON
Electric starter
START
Fig. 8-3
8-4 MODEL WITH OIL SENSOR
Yellow
To LED Lamp
Yellow / Red
Oil sensor
control unit
Orange
Orange
Oil
Black
sensor
Black / White
Body
earth
LA106
Black
To stop switch
Spark
plug
Oil sensor as option
Fig. 8-4
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9. ELECTRIC STARTER
EX 17, 21
9-1 SPECIFICATIONS
129.5
Pinion gear
Models EX17, 21
12
Model EX27
Voltage
Power
(V)
(kW)
(kg)
0.6
1.6
0.6
3.4
Weight
EX 27
PINION GEAR
157.8
Fig. 9-1
9-2 OPERATING PRINCIPLES
The battery is connected to the 6 or 8 mm diameter terminal of the magnetic switch.
The figure below shows the state when the starter is ON.
M
M
S
S
M
M
BATTERY
M
MAGNETIC
SWITCH
ELECTRIC STARTER
KEY SWITCH
Fig. 9-2
There are two energized circuits: the magnetic switch (M) circuit and the starter motor (S) circuit.When the key
switch is ON, the (M) circuit is closed, the current flows in the direction of the arrows, the coil of the magnetic
switch is magnetically excited and the contactor is pulled.
As a result, a low current flows through the (M) circuit and a high starter current flows through the (S) circuit.
This energizes the starter motor and cranks the engine.
Engagement of the pinion gear (EX17,21)
When the starter motor is started, the weight built into the spiral splines located on the shaft moves in the direction
of the axis driven by centrifugal force and pushes out the pinion gear, and the pinion gear engages the ring gear.
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9-3 COMPONENT PARTS
(Models EX17 and EX21)
PINION AY
FRONT COVER
MAGNETIC SWITCH
PINION
STOPPER SET
BATTERY
CABLE
THROUGH BOLT (2 pcs.)
O - RING
WASHER
YOKE AY
O - RING
ARMATURE AY
BRUSH
SPRING (BRUSH)
REAR COVER
BRUSH HOLDER
(Model EX27)
MAGNETIC SWITCH
PINION AY
ARMATURE AY
YOKE AY
SPRING (BRUSH)
BRUSH
CASE METAL
FRONT COVER
BRUSH HOLDER
REAR COVER
THROUGH BOLT (2 pcs.)
FRONT METAL
PINION STOPPER SET
Fig. 9-3
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10. OIL SENSOR
10-1 SPECIFICATIONS
Float type
(with lead switch incorporated)
Type
Resistance
(at FULL oil level)
100 M ohms or over
Operating
Temperature
OIL SENSOR
-30 to +180 degree Celsius
Fig.10-1
10-2 CONSTRUCTION AND OPERATION
The oil sensor is composed of the float, per manent
magnet incorporated into the float and the oil sensor.
In accordance with the oil level, the float moves up and
down.
When the oil level is upper level, the float moves up.
FLOAT
PERMANENT MAGNET
LEAD SWITCH
Fig.10-2
When the oil level is lower level, the float moves down.
The permanent magnet is close to the lead switch, and
the lead switch is activated by the magnetic force.
MAGNETIC FORCE
Fig.10-3
NOTE : With regards to the wiring diagram,
please refer to the section 8-4 (page52).
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11. AUTOMATIC DECOMPRESSION SYSTEM
11-1 FUNCTIONS AND CONSTRUCTION
EX series engines employ an automatic decompression system as a standard feature. This enables easy
starting of the engine, with lighter recoil pull.
The automatic decompression system releases the compression of the engine by lifting up the exhaust valve at
cranking speed.The following is the explanation of the function.
At the end of the compression process, the release lever lifts up the rocker arm (exhaust) which in turn opens
up the exhaust valve slightly to release the compression.
The release lever has a flyweight on its end and another end of the lever is a crescent cam.
When the engine is cranked, the crescent cam projects above the cam profile and lifts up the rocker arm
(exhaust) because the force of the return spring on the weight is larger than the centrifugal force on the weight.
ROCKER ARM
ROCKER ARM
(EXHAUST)
(EXHAUST)
ROCKER ARM
(INTAKE)
RELEASE LEVER
CAM
CRESCENT CAM
CAMSHAFT
RELEASE LEVER
A
DETAIL
A
Fig. 11-1
When the cranking speed reaches a specified r.p.m., the crescent cam is retracted under the cam profile
because the centrifugal force applied to the flyweight becomes larger than the force of the return spring on the
weight and thus it is shifted to the position shown in the illustration below.
RELEASE LEVER
ROCKER ARM
(EXHAUST)
ROCKER ARM
(EXHAUST)
ROCKER ARM
(INTAKE)
CAM
CRESCENT CAM
CAMSHAFT
A
RELEASE LEVER
DETAIL
A
Fig. 11-2
11-2 INSPECTION
When assembling the release lever, make sure that it works smoothly.
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12. CARBURETOR
12-1 SPECIFICATIONS
EX13
DUAL
EX17
DUAL
EX21
DUAL
83.8
EX27
DUAL
96.0
A/C Type
STD
STD
81.3
40.0
1-1/4
STD
86.3
41.3
1
STD
98.0
40.0
1-1/2
Main Jet
70.0
40.0
1-3/4
68.8
40.0
80.3
40.0
Pilot Jet
Pilot Screw Turning
12-2 FUNCTIONS AND CONSTRUCTION
12-2-1 FLOAT SYSTEM
The float chamber is located below the carburetor body.Through the operation of the float and the needle
valve, the float chamber maintains a constant fuel level while the engine is working.
The fuel flows from the tank into the float chamber through the needle valve. When the fuel rises to a
specific level, the float rises.When the buoyancy of the float is balanced with the fuel pressure, the needle
valve shuts off the fuel passage, thereby maintaining the fuel at the predetermined level.
12-2-2 PILOT SYSTEM
The pilot system supplies fuel to the engine during idling and low-speed operation.
Fuel is initially metered by the main jet and then metered once again by the pilot jet.At the pilot jet, the fuel
is mixed with air metered by the pilot air jet and then the fuel/air mixture is ef d to the engine through the pilot
outlet and the bypass. During idling, fuel is fed to the engine mainly through the pilot outlet.
12-2-3 MAIN SYSTEM
The main system feeds fuel to the engine at medium and high speed operation.
Fuel is metered by the main jet and flows into the main nozzle. Air metered by the main air jet is mixed with
fuel through the bleed holes of the main nozzle.The fuel/air mist is injected into theVenturi and mixed once
again with air from the air cleaner.This fuel/air mixture is now of optimum concentration and is fed into the
combustion chamber of the engine.
12-2-4 CHOKE SYSTEM
The choke system is for easier start of the engine in cold weather conditions.
When the engine is started with a closed choke, the negative pressure applied to the main nozzle increases.
This causes a larger amount of fuel to be drawn into the carburetor, which in turn makes it easier to start
the engine.
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FUEL SYSTEM OUTLINE
FUEL
NEEDLE
VALVE
FLOAT
FLOAT CHAMBER
Fig. 12-1
PILOT OUTLET
BYPASS
PILOT JET
PILOT AIR JET
MAIN NOZZLE
AIR INTAKE PORT
CHOKE VALVE
FLOAT
MAIN AIR JET
MAIN JET
Fig. 12-2
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12-3 DISASSEMBLY AND REASSEMBLY
Mechanical failures aside, most carburetor malfunctions occur when the fuel/air ratio of the mixture is not
correct. This is usually caused by clogged jets, air passages and fuel passages, or by variations in the fuel
level.
To get the best possible performance from the carburetor, ensure that the each passages are kept clean so that
air and fuel can flow freely through them.
MODEL EX13, 17, 21
MODEL EX27
21 20 19
18 21 20
13 14
18
17
16
24
23 22
25
26
22
23
27
28
26
25
24
14
13
1
1
12
12
11
2
3
11
10
3
10
4
4
5
5
6
7
9
8
6
7
9
8
Fig. 12-3
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The procedures for overhauling the carburetor are described below. (Refer to Fig. 11-3.)
12-3-1 THROTTLE SYSTEM
(1) When the throttle stop screw
is removed, the spring
can be taken out.
(2) Remove the phillips screw and the throttle valve , then take out the throttle shaft
When removing the throttle valve, take care not to damage the valve edge.
.
12-3-2 CHOKE SYSTEM
(1) Remove the choke valve . Then pull out the choke shaft
.
(2) When reassembling the choke shaft, be sure to position the cutout on the choke valve facing the pilot air
jet.
12-3-3 PILOT SYSTEM
(1) Remove the pilot jet . Use the correct tool so as to avoid damaging the jet.
(2) When reassembling the pilot jet, be sure to firmly tighten it, otherwise fuel may leak, leading to engine
malfunction.
12-3-4 MAIN SYSTEM
(1) Remove the bolt
and remove the float chamber body
.
(2) Remove the main jet
from the body
.
(3) Remove the main nozzle
from the body
.
(4) When reassembling the main system, be sure to fasten the main jet and main nozzle firmly to the body,
otherwise the fuel concentration in the fuel/air mixture may become too rich, leading to engine malfunction.
(5) The tightening torque of the bolt
washer.
is 9 N m (90 kgf cm / 6.5 ft lb.). Be sure not to forget to mount the
12-3-5 FLOAT SYSTEM
(1) Take out the float pin
and then remove the float
is linked to the float
and the needle valve
.
Since the needle valve
, take care when assemble.
Do not use drill or similar objects for cleaning the jets, as these are likely to damage the orifices, which
in turn can impair fuel flow. Use compressed air to clean the jets.
The float pin is pressed into the carburetor body. When removing the needle valve and the float, a rod
or a similar tool slimmer than the float pin should be used.Tap the reverse side gently and remove.
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13. RECOIL STARTER
13-1 RECOIL STARTER
Tools required: Screwdriver, pliers and protective glasses
NOTE:
Put on the protective glasses prior to start disassembly.
13-1-1 DISASSEMBLY PROCEDURE
(1) Release the reel spring power
-1 Hold the starter knob and pull out the star ter
rope.
-2 Pull out the rope fully and align the rope knot in
the reel with the rope guide.
-3 Hold the reel down firmly with both thumbs,
taking care not to allow it to spring back.
(Fig. 12-1)
-4 Remove the knot from the reel, untie the knot
and pull the rope out toward the starter knob.
Note:This procedure requires 2 people.
Fig. 13-1
-5 While controlling the reel with the thumbs, slowly
wind it back as far as it will go.
NOTE:
When the rope is pulled out to its full length,the force stored in the spring reaches its maximum.
Be careful not to drop it or release your grip on it suddenly.
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(2) Remove the components. (Fig. 13-2)
-1 Grip the case and loosen the set screw.
SET SCREW
-2 Take out the set screw, the ratchet guide,
the friction spring and the ratchet in that
order.
RATCHET
GUIDE
FRICTION
SPRING
(3) Remove the reel. (Fig. 13-2)
-1 Hold down the reel gently to keep it from
escaping from its case and rotate it slowly
back and forth by quarter turns until it moves
smoothly.
RATCHET
REEL
-2 Lift the reel up little by little and take it out of
the case.
-3 If the spring is about to pop out of the reel,
repeat steps (3)-1 and (3)-2.
STARTER CASE
NOTE:
Fig. 13-2
Since the spring is stored in the reel, make sure
not to drop or shake the reel after removing it.
Place it on a level surface such as a table.
Disassembly is completed.
NOTE:
Put on the protective glasses prior to start reassembly.
13-1-2 REASSEMBLY PROCEDURE
(1) Put the reel back into the case
GREASE
-1 Apply grease to the surface of the case.
(Fig.13-3)
-2 Adjust the position of the inner end of the
spring in the reel. (Fig. 13-4)
-3 Hold the reel in such a way that the inner end
of the spring hooks onto the shaft hook and
then place the reel carefully back into the case.
SHAFT HOOK
Fig. 13-3
Position where the inner end of the
spring touches to the rib of the bearing.
-4 Turn the reel gently countercloc kwise to
confirm that the spring is hooked.
Fig. 13-4
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(2) Mount the components
-1 Mount the ratchet into the reel. (Fig. 13-5)
THE RATCHET SHOULD
BE IN THE CLOSED POSITION
Fig. 13-5
-2 Mount the ratchet guide assembly, taking care
not to move the ratchet. (Fig.13-6)
Set screw
Ratchet
guide
Friction spring
Ratchet guide sub-assembly
Fig. 13-6
(3) Tighten the set screw
-1 Hold the ratchet guide gently by your hand to
prevent it from rotating, then tighten the set
screw.
APPR
ROPE HOLE IN REEL
FR
OM THOE
X.
200 MM
Tightening torque(M6)
REEL
5.5 N m
(55 kgf cm)
(4.0 ft lb.)
(4) Tension the reel spring
ROPE GUIDE
-1 Grip the case and tur n the reel 6 times
counterclockwise.
Fig. 13-7
-2 Fix the reel so that the rope hole in the reel is
aligned with the rope guide. (Fig. 13-7)
NOTE:
The spring force reaches its maximum value when the reel is wound up. Be careful not to drop
it or release your grip on it suddenly.
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(5) Install the rope
NOTE: This procedure requires 2 people.
-1 Pass the rope end through the rope guide and the
rope hole of the reel and pull through approximately
20 cm out of the reel. (Fig. 13-7)
Approx. 20mm
-2 Tie a knot in the rope end . (Fig. 13-8)
-3 Put the rope into the reel, taking care that the
rope end does not stick up. (Fig. 13-9)
-4 Grasp the rope fir mly with one hand at
approximately 50 cm from the rope guide and
keep the rope tense, taking care that the rope
is not pulled into the reel.
Fig. 13-8
-5 Release the reel carefully and allow the rope to
be wound back slowly by the force of the spring
until the knob reaches the rope guide.
Assembly is completed.
Fig. 13-9
The disassembly and the reassembly are completed, however, carry out the following to check if the necessary
components have surely been assembled.
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13-1-3 CHECKING THE RECOIL STARTER AFTER REASSEMBLY
(1) Pull the starter knob about 2-3 times.
(a) If the starter knob is too heavy to pull, check that each parts have been assembled as specified.
(b) If the ratchet does not work, check for missing parts such as the friction spring.
(2) Pull out the starter knob as far as it will go.
(a) If the starter rope remains in the rope slot in the reel, the spring may be over-stressed. To fix this, pull
out the starter rope approximately 30 cm, and, controlling the rotation of the reel with your thumb, allow
the starter rope to rewind about 1 or 2 turns.
(b) If the starter rope rewinds slowly or only partially, apply grease or oil to the rotary parts or the friction
surfaces. If this does not help, try winding up the spring 1 or 2 turns, taking care not to over-stress the spring.
(c) If there is a sound indicating that the spring is off the hook and the starter rope does not be wound
back, reassemble the recoil starter from the beginning.
13-1-4 OTHER GUIDES
SPRING
(1) If the spr ing escapes from the reel dur ing
disassembly
STARTER
REEL
(a) Hook the outer end of the spring onto the gap
in the reel, and rewind the spring, holding the
spring with your fingers so as to prevent it from
springing out of the housing unit.
(Wear protective gloves when doing this.)
Hook the outer end of the
spring onto the gap in the reel.
Fig. 13-10
(b) Hook the inner end of the spr ing onto the
projection on the starter case.
STARTER REEL
SPRING
Refer to the assembly procedure for more
details.
(2) About lubrication
Lubricate the rotating and frictional parts and the
spring with g rease (heat-resistant g rease
recommended) or engine oil when the star ter is
disassembled and prior to long term storage.
E
Y GREAS
APPL
STARTER CASE
Fig. 13-11
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14. INSTALLATION
Installation has a decisive influence on engine life, ease of maintenance and inspection, frequency of inspection
and repair, running costs and other related aspects. Before installing the engine, be sure to plan the installation
with care, taking the points below into account.
14-1 INSTALLING
When installing the engine, pay special attention to the position of installation, the method for coupling with
working equipment, and the foundations and supports for the engine. Position the engine so that tasks such as
gasoline and oil replenishment and inspection, spark plug inspection, air cleaner maintenance, oil drainage
and so on can be carried out as easily as possible.
14-2 VENTILATION
An engine requires fresh air for cooling and for burning fuel.When an engine is covered with a bonnet or is operated
in an enclosed space, the temperature around the engine rises and this causes such problems as vapor lock, oil
deterioration, increased oil consumption, power loss, engine seizure, and reduced engine life, making it difficult for
the engine to function normally. It is thus necessary to install ducts and dampers to guide fresh air, so as not to
recycle the hot air used to cool the engine and to prevent the working equipment from heating up.
Be sure to keep the engine room temperature below 50 C all year round and to prevent the accumulation of hot
air in the engine room.
14-3 EXHAUST EQUIPMENT
Exhaust gas is noxious. When operating the engine indoors, make sure that exhaust gases are discharged
outdoors. However, if the exhaust pipe is long, resistance increases and this lowers engine output.Therefore,
the longer the exhaust pipe the larger its inner diameter should be.
Exhaust pipe length:
Exhaust pipe length:
Less than 3 m
3 - 5 m
Pipe inner diameter:
Pipe inner diameter:
30 mm
33 mm
The ideal solution is forced exhaustion (outdoors) by installing a blower on the exhaust pipe.
Install a safety cover on the exhaust pipe, muffler and other related parts.
14-4 FUEL SYSTEM
If the fuel tank is detached from the engine, the height from the bottom of the fuel tank to the fuel joint of the
carburetor should be between 5 cm and 50 cm.
When using a fuel pump, the bottom of the fuel tank can be up to 20 cm below the carburetor. Position the fuel
tank carefully because, when it is low, fuel is not fed to the carburetor and when it is high, it can cause an
overflow in the carburetor. When piping the fuel, the hose should be as short as possible and attention should
be paid to heat transmission, size, bending, leakage at hose joints and so on. Care should also be taken to
prevent air lock and vapor lock.
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14-5 POWER TRANSMISSION TO DRIVE MACHINES
14-5-1 BELT DRIVE
Note the following:
• Use a V-belt rather than a flat belt.
• The drive shaft of the engine must be parallel to the drive shaft of the driven machine.
• The drive pulley of the engine must be in line with the driven pulley of the machine.
• Install the engine pulley as close to the engine as possible.
• If possible, span the belt horizontally.
• Disengage the load when starting the engine.
A belt tensioner or similar should be installed if no clutch is used.
14-5-2 FLEXIBLE COUPLING
When using a flexible coupling, run-out and misalignment between the driven shaft and the engine shaft
should be minimized.
The permissible margin of run-out and misalignment is specified by the flexible coupling manufacturer.
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15. TROUBLESHOOTING
If the engine shows any sign of malfunction, the cause should be determined immediately and appropriate
countermeasures should be taken to prevent the problem from worsening.This section describes certain known
problems, their possible causes and appropriate countermeasures. Note, however, that the list of problems
presented here is not all.Generally speaking, since there is the possibility of multiple causes of r a single problem,
please use your experience and common sense when deciding on what action to take.
15-1 ENGINE
The following three conditions must be fulfilled for satisfactory engine start.
1. The cylinder filled with a proper fuel-air mixture.
2. Good compression in the cylinder.
3. Good spark, properly timed, to ignite the mixture.
The engine cannot be started unless these three conditions are met. There are also other factors which
make engine start difficult, e.g., a heavy load on the engine when it is about to start at low speed, and a
high back pressure due to a long exhaust pipe.
Problem and possible cause
Remedy
1. Ignition system problems
1) Spark plug
Improper spark plug gap
Adjust the gap
Replace
Clean
Insulation defect
Carbon deposits
2) Ignition coil
Replace
Repair or replace
Insulation defect or discontinuity
Poor contact or broken wire
3) Improper air gap between ignition coil and flywheel Adjust
2. Fuel system problems
1) No fuel in fuel tank
Refill
2) Fuel hose clogged or pinched
3) Air in fuel lines
Clean or replace
Check and retighten joints
Replace
4) Poor quality gasoline or water in gasoline
5) Carburetor
Overflow
Adjust
Clogged or damaged
Throttle valve malfunction
(does not close fully)
Overhaul
Check and adjust
3. Engine core components 1) Insufficient tightening of cylinder head bolts
problems
Check and retighten
2) Wearing of piston, piston rings and/or cylinder Repair or replace
3) Improper contact of valve and seat
4) Valve sticking
Repair
Repair
5) Improper valve clearance
Adjust
6) Leakage from intake manifold gasket
7) Leakage from carburetor gasket
8) Insufficient tightening of spark plug
Retighten; replace gasket
Retighten; replace gasket
Retighten
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Problem and possible cause
Remedy
1. Insufficient compression 1) Loosen spark plug
Retighten; replace gasket
Retighten; replace gasket
Replace
2) Leakage from cylinder head gasket
3) Piston ring seizure or wear
4) Piston or cylinder wear
5) Incorrect valve and seat contact
6) Valve stem seizure
Repair or replace
Repair or replace
Repair or replace
Adjust
7) Improper valve clearance
2. Ignition system problems 1) Faulty spark plug
Replace
2) Faulty ignition coil
Replace
3) Improper air gap between ignition coil and
flywheel
Adjust
4) Demagnetization (flywheel magneto)
Replace
3. Fuel system malfunction 1) Carburetor clogged
Overhaul, clean
Clean or replace
Check and retighten joints
Replace
2) Fuel strainer and/or hose clogged
3) Air in fuel lines
4) Poor quality gasoline or water in gasoline
1) Air cleaner clogged
4. Low air intake volume
1. Engine
Clean or replace
Repair or replace
2) Throttle valve malfunction
1) Cooling air flow obstructed at inlet or cylinder
baffle portion
Clean
2) Poor quality engine oil
3) Lean fuel/air mixture
Replace
Check and adjust
carburetor
4) Excessive back pressure of exhaust system
5) Overloading
Check and clean or replace
Adjust to rated load
Adjust
1. Carburetor system
2. Intake system
1) Low idling speed
2) Slow system passage clogged
Check and clean
Check and tighten;
replace gasket
1) Air mixing from air intake system joints
3. Cylinder head
4. Valve system
1) Gasket faulty (blow-by)
1) Improper valve clearance
2) Leakage from valve seat
Replace
Adjust
Repair
3) Excessive clearance between valve stem and
guide
Replace
5. Ignition system
Check; adjust or replace
plug
1) Weak spark
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Problem and possible cause
1) Loose oil drain plug
Remedy
1. Oil leakage
Tighten
Replace
Tighten
Replace
Replace
2) Faulty oil drain gasket
3) Loose main bearing cover bolts
4) Faulty main bearing cover gasket
5) Crankshaft oil seal (front, rear) defect
2. Oil up
1) Faulty piston oil ring
Replace
Replace
Replace
Replace
2) Piston ring seizure, wear or poor contact
3) Excessive wear of piston and/or cylinder
4) Faulty stem seal
5) Excessive oil level
Adjust oil level
6) Breather defect
Repair or replace
Clean or replace
1. Fuel system
1) Clogged air cleaner
2) Faulty needle valve and/or high fuel level in
float chamber
Repair or replace
3) Choke does not open fully
1) Low compression
Repair or replace
Check and repair
2. Engine core components
Check and adjust load
and/or engine speed
2) Overcooling
1. Ignition system problems
2. Fuel system problems
1) Loose ignition system wiring
2) Improper or faulty spark plug
Inspect and tighten
Clean or replace
Clean, adjust or replace
carburetor
1) Lean or rich fuel/air mixture
2) Carburetor contamination
Overhaul or clean
Clean or replace
Tighten; replace gasket
Clean
3) Dirty or clogged fuel lines
4) Air mixing from air intake system joints
1) Carbon deposit in combustion chamber
2) Leakage from cylinder head gasket
1) Improper valve clearance
3. Cylinder head
Replace
4. Valve system problems
Adjust
2) Valve heat deterioration
Replace
3) Worn or broken valve spring
4)Improper valve timing
Replace
Adjust
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ELECTRIC STARTER
Engine does not start
Check battery charged
state and battery terminal
connection or corrosion
for any abnormality.
Charge or replace the battery.
Repair connection or
corrosion of battery terminals.
NG
NG
NG
NG
Does the
crank run?
Does the
starter run?
Key switch
Connected state
Check/repair wiring to the
starter magnetic switch.
Repair or replace starter
magnetic switch.
OK
Operation sound of
magnetic switch of starter
OK
OK
Check settling of spring and
sliding of pinion.
Replace if pinion/ring gear
end face is worn.
OK
NG
NG
Check engagement of
pinion and ring gear
Correction of pinion gap
OK
With starter alone, connect
the battery (+) terminal
and the M or K terminal of
the starter and check if
motor runs.
Replace motor
(brush holder or armature).
Check pinion roller clutch
for damage or replace.
OK
OK
Check battery charged
state and battery terminal
connection or corrosion
for any abnormality.
There is any contact
failure of starter magnetic
switch. Please replace.
NG
(Too slow)
Check battery charged
state and battery terminal
connection or corrosion
for any abnormality.
Charge or replace the battery.
Repair connection or
corrosion of battery terminals.
NG
Normal rotation?
OK
OK
Check ignition system
and fuel system.
Check viscosity of engine
oil for any abnormality.
NG
NG
Change the engine oil.
OK
Replace the starter with a
new one and check if it
runs.
Check the engine interior.
S
M
OK
Repair or replace the
starter.
B
K
When the starter continuously runs
(Immediately remove the (-) terminal of the battery)
Motor does not stop even
when the key switch is
turned off.
Repair or replace the key switch
or starter magnetic switch.
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Problem and check item
Description
Check S terminal and B terminal
Remedy
1. Checking of
continuity of
wiring
(1) When no voltage is applied to the S
terminal and B terminal, check
continuity of the terminals and key
switch and repair or replace if
necessary.
for deformation, looseness,
rusting, or dust sticking.
KEY SWITCH
Carefully check inserting
method of the S terminal.
If not abnormal, set the key
switch to START position while
cranking (no ignition of engine)
and check if voltage is applied
to the S terminal and B terminal
of starter motor.
(+)
S
(-)
B
(2) If voltage is applied to the S terminal
and B terminal, go to “2. Battery
checking.”
K
M
Check battery voltage and specific
gravity of battery fluid.
[Voltage]
2. Battery checking
(1) Charge or change the batter y when
voltage is lower than 12.4V or specific
gravity is lower than 1.22 (at 20 C).
Normal value : 12.4 to 12.8V
Limit (charging required): 12.4V
or lower
(2) If the wiring and battery are normal,
remove the star ter and go to “3.
Checking of pinion operation.”
GRAVITY METER
Staring limit : 12V (at 20 C)
[Specific gravity]
Normal value : 1.22 to 1.29
Limit (Charging required)
: 1.22 or lower
BATTERY
[Service life]
Variance in specific gravity
among cell
: 0.04 or more
(1) If the pinion operates or contactor sound
is heard, step to “4. Checking of
magnetic switch (1).”
3. Checking of
Check if the pinion operates or
pinion operation sound of magnetic switch
contactor is heard.
If the pinion does not operate
or magnetic switch sound is not
heard, check continuity of each
coil of magnetic switch.
(2) In case of no continuity
Replace the magnetic switch.
(3) When continuity is OK
Step to “4. Checking of magnetic switch
(2).”
4. Checking of
magnetic
switch
(1) Operate the magnetic switch
and check B-M terminals
(1) In case of no continuity
Contact continuity failure. Replace the
magnetic switch.
(2) When continuity is OK
Step to “5. Motor checking.”
(2) Check the magnetic s witch
plunger and bobbin interior for
dust sticking or rusting.
(1) Clean the plunger. If the bobbin interior
is contaminated, replace the magnetic
switch.
5. Motor checking
Connect the (+) side of the
battery to the M ter minal of
magnetic switch and check if the
motor runs.
(1) If the motor does not run, check electric
circuit inside the motor , field coil,
armature, and brush and replace faulty
parts.
(+)
(
-)
M
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Problem and check item
Description
Motor idles and engine does not
Remedy
(1) Remove and check the starter. Check
or replace the pinion clutch if
necessary.
Check engaged
state of pinion and
ring gear.
run.
(2) Check battery charged state and
battery terminal connection or
corrosion for any abnormality.
If pinion and r ing gear do not
engage with each other and
abnormal noise is heard between
end faces of pinion and ring gear,
check the starter pinion and ring
gear.
(1) Remove the starter and check pinion
and ring gear end f aces. If worn,
replace the pinion and ring gear.
(2) In case of sliding fault of the pinion,
correct it.
RING GEAR
PINION GEAR
(3) If shift lever or spring is deformed,
replace it.
(3) Both starter
and engine run,
but the engine
does not start.
Check if the rotation speed is
normal or slow. If slow, check the
battery and engine oil viscosity.
(1) When the rotation speed is normal
Check the ignition system and fuel
system.
(2) When the rotation speed is slow
(a) Check the battery.
(b) Check the viscosity of engine oil. If
not normal, change the oil.
(c) If both (a) and (b) are normal
Remove and check the starter.
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16. STANDARD REPAIR TABLES
“STD” in the following table is the parts dimension from the brand new engine or the spare parts.
Whereas, “Limit” shows the maximum allowance for the parts to be used on the engine.
If the measurement exceeds beyond the “Limit”, the part needs to be replaced and/or repaired.
16-1 STANDARD DIMENSIONS AND LIMITS OF USE
Unit: mm (in.)
ITEM
STD
Limit
CYLINDER HEAD
* Flatness
EX13
EX17
EX21
EX27
0.05
(0.002)
0.1
(0.004)
* Intake/exhaust valve seat
contact width
EX13
EX17
EX21
EX27
Intake
Exhaust
0.7 - 1.0
(0.0276 - 0.0394)
-
* Intake/exhaust valve guide inner diameter
EX13
EX17
EX21
EX27
Intake
Exhaust
5.500 - 5.518
(0.2165 - 0.2172)
-
* Rocker arm pin outer diameter
EX13
EX17
EX21
EX27
D1
D2
Pin outer
diameter
5.970 - 5.980
(0.235 - 0.235)
5.9
(0.232)
D
1, D2
* Rocker arm pin support inner diameter
D
3
D4
Support
inner
diameter
EX13
EX17
EX21
EX27
6.00 - 6.018
(0.236 - 0.237)
6.05
(0.238)
D
3, D4
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Unit: mm (in.)
ITEM
STD
Limit
CYLINDER
* Inner diameter
58.000 - 58.019
(2.2835 - 2.2842)
EX13
To be rebored when
the difference between
max. and min. of
diameter reached to
0.1 (0.004).
EX17
EX21
67.000 - 67.019
(2.6378 - 2.6385)
Standard
75.000 - 75.019
(2.9528 - 2.9535)
EX27
EX13
58.250 - 58.269
(2.2933 - 2.2941)
First
reboring
EX17
EX21
67.250 - 67.269
(2.6476 - 2.6484)
Ditto
Ditto
75.250 - 75.269
(2.9626 - 2.9633)
EX27
EX13
58.500 - 58.519
(2.3031 - 2.3039)
Second
reboring
EX17
EX21
67.500 - 67.519
(2.6575 - 2.6582)
75.500 - 75.519
(2.9724 - 2.9732)
EX27
EX13
EX17
EX21
EX27
Less than 0.01
(0.0004)
* Roundness after reboring
EX13
EX17
EX21
EX27
Less than 0.015
(0.0006)
* Cylindricity after reboring
PISTON
* Outer diameter at skirt in thrust
direction
57.980 - 58.000
(2.2827 - 2.2835)
57.89
(2.2791)
EX13
EX17
EX21
66.960 - 67.000
(2.6362 - 2.6378)
66.88
(2.6331)
Standard
74.980 - 75.000
(2.9520 - 2.9527)
74.89
(2.9484)
EX27
EX13
58.230 - 58.250
(2.2925 -2.2933)
58.14
(2.2890)
Oversize
+0.25
EX17
EX21
67.210 - 67.250
(2.6461 - 2.6476)
67.13
(2.6429)
75.230 - 75.250
(2.9618 - 2.9626)
75.14
(2.9583)
EX27
EX13
58.480 - 58.500
(2.3024 - 2.3032)
58.39
(2.2988)
Oversize
+0.50
EX17
EX21
67.460 - 67.500
(2.6559 - 2.6575)
67.38
(2.6528)
75.480 - 75.500
(2.9717 - 2.9724)
75.39
(2.9681)
EX27
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Unit: mm (in.)
ITEM
STD
Limit
EX13
EX17
EX21
EX27
PISTON
* Ring groove side clearance
Top
Second
0.15
(0.0059)
0.035 - 0.080
(0.0014 - 0.0031)
0.02 - 0.075
(0.0008 - 0.0031)
EX13
Oil ring
Coil exp
EX17
EX21
0.15
(0.0059)
0.01 - 0.065
(0.0004 - 0.0026)
0.01 - 0.065
EX27
EX13
(0.0004 - 0.0026)
0.060 - 0.165
(0.0024 - 0.0065)
Oil ring
(three-piece)
EX17
EX21
0.0300 - 0.185
(0.0012 - 0.0073)
-
0.0100 - 0.205
(0.0004 - 0.0081)
EX27
EX13
* Piston pin hole
12.991 - 13.009
(0.5115 - 0.5122)
13.035
(0.5132)
EX17
EX21
15.991 - 16.009
(0.6296 - 0.6303)
16.035
(0.6313)
17.991 - 18.009
(0.7083 - 0.7090)
18.035
(0.7224)
EX27
EX13
* Piston pin outer diameter
12.992 - 13.000
(0.5115 - 0.5118)
12.960
(0.5102)
EX17
EX21
15.992 - 16.000
(0.6296 - 0.6299)
15.960
(0.6283)
17.992 - 18.000
(0.7083 - 0.7087)
17.960
(0.7071)
EX27
EX13
* Clearance between piston and cylinder
at skirt
0.040 - 0.079
(0.0016 - 0.0031)
0.25
(0.010)
EX17
EX21
EX27
0.050 - 0.089
(0.0020 - 0.0035)
0.15 - 0.35
(0.0059 - 0.0138)
* Piston ring end gap
EX13
Top
EX17
EX21
0.15 - 0.3
(0.0059 - 0.0118)
1.5
(0.0591)
0.1 - 0.3
(0.0039 - 0.0118)
EX27
EX13
0.15 - 0.35
(0.0059 - 0.0138)
1.5
(0.0591)
Second
EX17
EX21
EX27
0.2 - 0.4
(0.0078 - 0.0157)
0.2 - 0.4
(0.0078 - 0.0157)
EX13
Oil
(Coil exp)
EX17
EX21
0.05 - 0.25
(0.0020 - 0.0098)
1.5
(0.0591)
0.1 - 0.3
(0.0039 - 0.0118)
EX27
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Unit: mm (in.)
ITEM
STD
Limit
CONNECTING ROD
* Large end inner diameter
EX13
EX17
EX21
30.000 - 30.016
(1.1811 - 1.1817)
30.1
(1.1850)
34.500 - 34.516
(1.3386 - 1.3392)
34.1
(1.3425)
EX27
* Clearance between large
end and crank pin
EX13
EX17
EX21
EX27
0.020 - 0.049
(0.0008 - 0.0019)
0.2
(0.0078)
* Small end inner diameter
13.010 - 13.021
(0.5122 - 0.5126)
13.08
(0.5150)
EX13
EX17
EX21
16.010 - 16.021
(0.6303 - 0.6307)
16.08
(0.6331)
18.010 - 18.021
(0.7091 - 0.7095)
18.08
(0.7118)
EX27
* Clearance between small
end and piston pin
EX13
EX17
EX21
EX27
0.010 - 0.029
(0.0004 - 0.0011)
0.12
(0.0047)
* Large end side clearance
EX13
EX17
EX21
EX27
0.100 - 0.780
(0.0040 - 0.307)
1.0
(0.0394)
CRANKSHAFT
* Crank pin outer diameter
EX13
EX17
EX21
29.967 - 29.980
(1.1798 - 1.1803)
29.85
(1.1752)
34.467 - 34.480
(1.3570 - 1.3575)
34.35
(1.3524)
EX27
EX13
EX17
EX21
* Journal outer diameter
27.988 - 27.997
(1.1019 - 1.1022)
D1
D2
29.988 - 29.997
(1.1806 - 1.1810)
EX27
EX13
EX17
EX21
D1
D2
24.988 - 24.997
(0.9838 - 0.9841)
29.988 - 29.997
(1.1806 - 1.1810)
EX27
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Unit: mm (in.)
ITEM
STD
Limit
CAMSHAFT
* Cam peak height (intake and exhaust)
EX13
EX17
EX21
EX27
Cam peak
height
29.028 - 29.128
(1.1428 - 1.1468)
28.98
(1.1409)
EX13
EX17
EX21
EX27
Cam inner
diameter
9.0 - 9.036
(0.3543 - 0.3557
9.05
(0.3563)
)
D
1,D2
* Cam sprocket inner diameter
* Pin (cam sprocket) outer diameter
EX13
EX17
EX21
EX27
Pin outer
diameter
8.95
(0.3524
8.953 - 8.975
(0.3525 - 0.3533)
D3
D4
D1
D2
)
D
3,D4
INTAKE/EXHAUST VALVES
* Valve stem outer diameter
EX13
EX17
EX21
EX27
5.440 - 5.455
(0.2142 - 0.2148)
5.35
(0.2106)
Intake
Exhaust
Intake
EX13
EX17
EX21
EX27
5.426 - 5.444
(0.2136 - 0.2143)
5.35
(0.2106)
* Clearance between valve stem and
valve guide
EX13
EX17
EX21
EX27
0.045 - 0.078
(0.0018 - 0.0031)
0.3
(0.0118)
EX13
EX17
EX21
EX27
0.056 - 0.092
(0.0022 - 0.0036)
0.3
(0.0118)
Exhaust
Intake
* Valve clearance (in cold state)
EX13
EX17
EX21
EX27
0.12 - 0.15
(0.0047 - 0.0059)
EX13
EX17
EX21
EX27
0.12 - 0.15
(0.0047 - 0.0059)
Exhaust
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Unit: mm (in.)
ITEM
VALVE SPRING FREE LENGTH
STD
Limit
EX13
EX17
EX21
EX27
27.4
(1.0787)
VALVE SEAT ANGLE
(INTAKE AND EXHAUST)
* Valve cutter angle (a)
* Valve contact width (b)
EX13
EX17
EX21
EX27
a: 90°
b: 0.7 - 1.0
(0.0276 - 0.0394)
Intake
Exhaust
2.0
(0.0787)
CHAIN LENGTH
263.1
(10.3583)
266.0
(10.4726)
EX13
EX17
EX21
EX27
160N (16kgf.)
F
269.0
(10.5906)
272.1
(10.7126)
L
281.7
(11.0906)
284.9
(11.2165)
L
307.1
(12.0906)
310.6
(12.2284)
EX13
3.5
EX17
EX21
EX27
4.0
2
Compression pressure
Fuel consumption
(kg cm / 500 rpm)
4.0
1.6
4.0
1.9
Continuous load / 3600 rpm (L / Hr)
1.2
2.6
Capacity
Efficacy
(L)
0.6
1.0
Lubricant
(mL)
350
5 - 10
500
8 - 13
Consumption
(mL / Hr)
Oil consumption has been measured under-following condition :
Good break-in operation has been finished.
Oil : 10W-30 (Grade SE)
Load : Continuous load / 3600 rpm
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16-2 TIGHTENING TORQUE
Tightening Torque
ITEM
N
m
kgf cm
ft lb.
Re-use
25.0 - 27.0
250 -270
18.1 - 19.5
When replace to new
cylinder head and
flange bolts
M8 × 68 flange bolt
Cylinder head bolts
28.0 - 30.0 280 - 300 20.3 - 21.7
M8 × 35 flange bolt
EX13,17,21
EX27
17.0 -19.0
170 - 190 12.3 - 13.7
9.4 - 10.8
13.0 - 15.0 130 - 150
Connecting rod cap
bolts
17.0 - 20.0 170 - 200 12.3 - 14.5
59.0 - 64.0 590 - 640 42.7 - 46.3
Flywheel nut
Main bearing cover bolts
22.0 - 24.0 220 - 240
12.0 - 15.0 120 - 150
23.0 - 27.0 230 - 270
16.2 - 17.7
8.7 - 10.8
16.6 - 19.5
New
Spark plug
Re-tightening
Muffler nut
Ignition coil
18.0 - 22.0 180 - 220 13.0 - 15.9
7.0 - 9.0 70 - 90 5.1 - 6.5
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17. MAINTENANCE AND STORAGE
The maintenance jobs described below apply to correct use of the engine under normal conditions.
The maintenance intervals mentioned in this section are not a guarantee that no maintenance is required
during those intervals.
For example, when the engine is used in dusty conditions, the air cleaner should be cleaned every day,
rather than every 100 hours.
17-1 DAILY MAINTENANCE (EVERY 8 HOURS OF USE)
MAINTENACE ITEMS
(1) Clean dust from engine.
REASON / REMARKS
(1) Dust can impair operation of various parts.
Governor linkage is especially sensitive to dust.
(2) Check for fuel leakage. Tighten or replace parts,
if necessary.
(2) Uneconomical and dangerous.
(3) Looseness can result in vibration and
accidents.
(3) Check all parts are securely fastened. Tighten,
if necessary.
(4) Check oil level and add up to full mark.
(4) Running the engine with insufficient oil can
result in serious problems, including engine
seizure.
(5) Check that the air cleaner element is clean.
Clean or replace, if necessary.
(5) A clogged air cleaner can cause power loss
and malfunction.
17-2 INSPECTION AND MAINTENANCE AFTER THE FIRST 20 HOURS
MAINTENACE ITEMS
(1) Change the crankcase oil.
REASON / REMARKS
(1) Sludge is deposited during running-in.
17-3 INSPECTION AND MAINTENANCE EVERY 100 HOURS (EVERY 10 DAYS)
MAINTENACE ITEMS
(1) Change the crankcase oil.
REASON / REMARKS
(1) Contaminated oil quickens wear.
(2) A clogged air cleaner can cause engine
malfunction.
(2) Clean the air cleaner.
(3) Inspect the spark plug. Clean with gasoline or
polish with sandpaper if dirty.
(3) A faulty spark plug can cause low power output
and poor starting performance.
17-4 INSPECTION AND MAINTENANCE EVERY 100 TO 200 HOURS (EVERY MONTH)
MAINTENACE ITEMS
REASON / REMARKS
(1) Clean the fuel strainer and fuel tank.
(1) Contaminated fuel can cause engine
malfunction.
(2) Change the air cleaner element.
(2) A clogged air cleaner can cause engine
malfunction.
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17-5 INSPECTION AND MAINTENANCE EVERY 300 HOURS
MAINTENACE ITEMS
REASON / REMARKS
(1) Inspect the intake and exhaust valve clearance.
Adjust if necessary.
(1) Incorrect clearance can cause low power output
and engine malfunction.
17-6 INSPECTION AND MAINTENANCE EVERY 500TO 600 HOURS (EVERY 6 MONTHS)
MAINTENACE ITEMS
(1) Remove the cylinder head and remove any carbon. (1) Carbon deposits can cause engine malfunction.
(2) Disassemble and clean the carburetor. (2) A faulty carburetor can cause engine malfunction.
REASON / REMARKS
17-7 MAINTENANCE EVERY 1,000 HOURS (ANNUAL MAINTENANCE)
MAINTENACE ITEMS
REASON / REMARKS
(1) Overhaul the engine. Clean and correct the
engine parts, replacing if necessary.
(2) Replace the piston rings.
(1) Dirty, misaligned or worn parts can cause low
power output and engine malfunction.
(2) Faulty piston rings can cause low output power
and engine malfunction.
(3) Replace the fuel hose.
(3) To prevent fuel leakage and attendant dangers.
17-8 ENGINE STORAGE
(1) Carry out the maintenance jobs described in step 16-1 above.
(2) Drain fuel from the fuel tank and carburetor float chamber.
(3) To prevent rust in the cylinder bore, inject oil through the spark plug hole, pull the recoil starter knob
gently 2 or 3 times and then put back the spark plug.
(4) Pull the recoil starter knob until the resistance is heavy. Leave it in that position.
(5) Clean the exterior of the engine with an oiled cloth.Place a plastic cover or similar over the engine, and
store the engine in a dry place.
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SERVICE INFORMATION
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PREFACE
This portion of the manual covers the service information, trouble shooting procedures of the
EX21 E FI (Electronic Fuel injection) engine.
Careful observance of the instructions given herein will result in better, safer and faster
service work.
For more detailed instructions of disassembling and reassembling procedures, please
refer back to the standard service procedure .
CONTENTS
Section
Title
Page
1. SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
2. DESCRIPTION OF FUEL SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
3. DISASSEMBLY AND REASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
3-1 PREPARATIONS AND PRECAUTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
3-2 SPECIAL TOOLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
3-3 DISASSEMBLY PROCEDURES (DIFFERENCE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
3-4 REASSEMBLY PROCEDURES (DIFFERENCE). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
4. WIRING DIAGRAM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
5. THROTTLE BODY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
5-1 SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
5-2 FUNCTIONS AND CONSTRUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
5-3 FUEL SYSTEM OUTLINE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
5-4 FUEL SYSTEM TESTING AND DIAGNOSIS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
6. INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
6-1 FUEL SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
7. TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
7-1 ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
8. MAINTENANCE AND STORAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
9. ORGANIZE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
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1. SPECIFICATIONS
Model
EX21D
Air-Cooled, 4-Cycle, Slant Single-Cylinder,
Horizontal P.T.O. Shaft, OHC Gasoline Engine
Type
Bore & Stroke
mm (in.)
67 x 60 (2.64 x 2.36)
211 (12.87)
8.5
Piston Displacement
Compression Ratio
ml (cu.in.)
3.2(4.4)/3000
3.7(5.0)/3600
Continuous Output
kW(HP)/r.p.m.
kW(HP)/r.p.m.
Maximum Output
Maximum Torque
5.1(7.0)/4000
‡
N m / r.p.m.
‡
(kgf m / r.p.m.)
‡
(ft lb. / r.p.m.)
13.9/2500
(1.41/2500)
(10.26/2500)
Direction of Rotation
Valve Arrangement
Cooling System
Counterclockwise as viewed from the P.T.O. shaft side
Overhead cam system
Forced air cooling system
Lubrication System
Splash lubrication system
Automobile engine oil ; Grade SE or higher (SG,SH or SJ in recomended)
SAE 10W-30-----Under ordinary atmospheric temperatures
SAE 5W-30-------In cold areas
Lubricant
Capacity of Lubricant
Throttle body
L
0.6
Electronic Fuel injection
Automobile unleaded gasoline
367 (270) at continuous rated output
Diaphragm pump (Pulse type)
3.6
Fuel
‡
g/kW h (g/HP h)
‡
Fuel Consumption Rate
Fuel Supply System
Fuel Tank Capacity
Ignition System
Spark Plug
L
Transistorized magneto
NGK BR-6HS
Starting System
Governor System
Dry Weight
Recoil starter
Centrifugal flyweight system
16 (35.28)
kg (lb.)
Dimensions (L x W x H)
mm (in.)
321 x 369 x 335 (12.6 x 14.5 x 13.2)
- 1 -
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2. DESCRIPTION OF FUEL SYSTEM
This engine is equipped with electronic fuel
injection.
THROTTLE BODY AY
i
The fuel system consists of a throttle body
assembly, power generation module, wire
harness, crankcase air pulse hose, fuel pressure
return pipe and a fine mesh fuel filter.
Throttle body assembly
WIRE HARNESS CP
POWER COIL CP
Power generation module
Wire harness
FUEL TANK CP
FUEL PIPE
(RETURN)
ELBOW
FUEL PIPE
(FUEL INLET)
SUS MESH
UNION
(FINE MESH FUEL FILTER)
Cylinder head air pulse hose
Fuel pressure return pipe and a fine mesh fuel filter
The fuel system is calibrated after careful testing for optimum all-round performance (including
starting, acceleration, fuel consumption, output power characteristics). Special attention is also
paid to the general-purpose use of the engine.
(For further information, refer to page 9, section “5.THROTTLE BODY”.)
- 2 -
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3. DISASSEMBLY AND REASSEMBLY
3-1 PREPARATIONS AND PRECAUTIONS
(1) When disassembling the engine, memorize the location of each part so that you can
reassemble the engine correctly. If necessary, attach identification tags with the required
assembly information to the parts.
(2) Store groups of parts in separate boxes. This will make reassembly easier.
(3) To prevent parts from being mislaid, keep each group provisionally assembled after
removing the parts from the engine.
(4) Handle the disassembled parts with the utmost care. Clean them with cleaning oil if
necessary.
(5) Use the correct tools in the correct way when disassembling and reassembling the engine.
3-2 SPECIAL TOOLS
Description
Parts number
Flywheel puller for pulling off the flywheel
Commercially available product
FLYWHEEL PULLER
Dwyer #490-1 Wet
XXXXXXXX
308802006
Wet handheld manometer
Throttle body
Computer data cable with 9 volt battery
Diagnostic EFI Compact Disc
Desktop or laptop computer
XXXXXXXX
RS232 9-pin COM port on computer
- 3 -
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3-3 DISASSEMBLY PROCEDURES (DIFFERENCE)
Step Parts to remove
Renarks and procedures
(1) Drain fuel from the tank.
Parts Fasteners
Fuel tank
10 mm spanner or box wrench
(2) Remove the fuel tank mounting nuts and bolts from
the crankcase.
M6 nut : 2 pcs.
M6 × 25mm : 1 pc.
(3) Disconnect the fuel pipe from the tank outlet.
(See Fig. 3-1)
7
(4) Disconnect the fuel return line from the bottom of the
fuel tank. (See Fig. 3-1)
(5) Remove the fuel tank from the crankcase
FUEL PIPE
(RETURN)
FUEL PIPE
(FUEL INLET)
FUEL TANK CP
To throttle body
(Return)
UNION
(FINE MESH FUEL FILTER)
To throttle body
(Inlet fuel)
Fig. 3-1
FUEL TANK
STEP 7
M6 x 25 BOLT : 1 pc.
M6 NUT : 2 pcs.
- 4 -
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Step Parts to remove
Renarks and procedures
Parts Fasteners
Throttle body,
Insulator
(1) Disconnect the fuel pump pulse line from the throttle body.
(2) Leaving the wire harness plugged into the throttle body, disconnect
the EFI wire harness from the engine.
(3) Remove the harness ground (black) from the top of the crankcase. M5 tapping screw
+ screwdriver
(4) Disconnect the engine temperature sensor (yellow) from the back
of the throttle bracket.
10mm box spanner
M6 × 12mm : 2 pcs
10
(5) Disconnect the low oil sensor lead (orange) and the power
generation lead (red) from the harness.
(6) Once the wire harness is completely free from the engine, remove
the throttle body with wire harness from the cylinder head.
Remove the insulator.
WIRE HARNESS
M5 TAPPING
SCREW
M6×12 BOLT
THROTTLE BODY
GASKET
GASKET
INSULATOR
FUEL PUMP
PULSE LINE
STEP 10
- 5 -
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Step
Parts to remove
Renarks and procedures
Parts Fasteners
EFI power generation module Remove the EFI power generation modudle.
M6 × 20mm : 2 pcs.
+ screwdriver
17
POWER COIL CP
VIEW A
SCREW AND WASHER AY
A
POWER COIL CP
STEP 17
- 6 -
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3-4 REASSEMBLY PROCEDURES (DIFFERENCE)
(22) THROTTLE BODY
(a) Replace the gasket of insulator with a new one and mount the insulator on the cylinder head
intake side.
(b) Mount the throttle body keeping the wire harness plugged into the throttle body.
Re-connect the fuel pump pulse line from the throttle body. Leaving the wire harness plugged
into the throttle body, re-connect the EFI wire harness to the engine. Connect the harness
ground (black) to the top of the crankcase.
Connect the engine temperature sensor (yellow) to the back throttle bracket mounting hole on
top of the throttle bracket. Connect the low oil sensor lead (orange) and the power generation
lead (red) to the harness.
ECU
Injection
Yellow:
Speed control
bracket
A
THROTTLE BODY
Air
Ignition coil
cleaner
Black:
(Earth wire)
side
Engine
side
Black:
Stop switch
Red:
Power coil
Orange:
Oil sensor
Pulse
Fuel
injection
Wire harness
Outlet
injection
Return
Return to
fuel tank
Inlet to
fuel pump
Inlet fuel
VIEW A
(26) FUEL TANK
(1) Connect the fuel pipe and fix it with a clamp.
(2) Connect the fuel pressure return pipe and fix it with a clamp.
(3) Mount the fuel tank on the crankcase.
- 7 -
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4. WIRING DIAGRAM
MODEL WITH EFI
Spark plug
Black
Ignition coil
Throttle body
EFI system
Power coil
Red
Orange
Fuel
injection
Oil sensor
Yellow
Temperrature sensor
Throttle bracket
Crankcase
- 8 -
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5. THROTTLE BODY
5-1 SPECIFICATIONS
This engine is equipped with electronic fuel injection.
The fuel system consists of a throttle body assembly, power generation module, wire harness,
crankcase air pulse hose, fuel pressure return pipe and a fine mesh fuel filter.
The fuel system is calibrated after careful testing for optimum all-round performance (including
starting, acceleration, fuel consumption, output power characteristics).
The throttle body monitors air and engine temperature at start up and performs the choke
function automatically.
While the engine is in operation, the throttle body monitors engine speed, throttle position,
intake air temperature, and engine temperature to ensure proper engine performance.
5-2 FUNCTIONS AND CONSTRUCTION
5-2-1 FUEL PUMP
The fuel pump chamber is located below the throttle body.
The fuel pump is actuated by crankcase vacuum from the cylinder head nipple through the
crankcase air pulse hose, to a nipple located on the fuel pump.
The fuel flows from the tank into the fuel pump. When the fuel pump is actuated by the
crankcase vacuum, the fuel is pressurized by the pump and pushed into the throttle body
pressure port.
5-2-2 FUEL PRESSURE REGULTOR
After the fuel pressure port is a diaphragm-type fuel pressure regulator.
The fuel pressure regulator relieves the throttle body of any excess fuel pressure and returns
excess fuel pressure back to the fuel tank through the fuel pressure return pipe.
5-2-3 FUEL INJECTOR
The throttle body pressure port feeds fuel at a regulated pressure to the fuel injector.
Fuel is metered by the fuel injector that is actuated electronically by the Electronic Control Unit (ECU).
The fuel is injected into the throttle bore and mixed with air from the air cleaner.
5-2-3 ELECTRONIC CONTROL UNIT (ECU)
The ECU (electronic control unit) on top of the throttle body is powered by the power generation
module when the engine is first rotated on start-up.
The ECU monitors engine conditions such as engine speed, throttle position, intake air
temperature, and engine temperature.
With these inputs, the ECU actuates the fuel injector to ensure the fuel/air mixture is of optimum
concentration and is fed into the combustion chamber of the engine at the correct timing.
The ECU also controls the low oil sensor system and monitors engine hours and other critical
engine data.
- 9 -
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5-2-4 POWER GENERATION MODULE
The power generation module is installed under the flywheel. This module provides power to
the ECU.
5-2-5 WIRE HARNESS
The wire harness for the EFI system connects key system components to the ECU.
The EFI wire harness contains a temperature sensor that measures engine temperature.
The ECU uses this input to adjust to engine conditions.
5-2-6 CHOKE SYSTEM
The throttle body monitors air and engine temperature at start up and performs the choke
function automatically.
The choke system automatically adjusts for easier start of the engine in all weather conditions.
5-3 FUEL SYSTEM OUTLINE
ECU
PULSING PRESSURE
TANK
FILTER
PIPE
FUEL PUMP
FUEL INJECTION
COMBUSION
FUEL RETURN PIPE
5-4 FUEL SYSTEM TESTING AND DIAGNOSIS
Most fuel system malfunctions occur when the fuel/air ratio of the mixture is not correct.
This is usually caused by clogged fuel filters, air passages, fuel passages, or by variations in
the fuel level.
To get the best possible performance from the throttle body, make sure that the fuel feed and
air feed passages are free so air and fuel can flow freely through them.
The procedure for inspecting the fuel system is described below.
Run all system tests with a full tank of fresh, clean fuel.
- 10 -
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5-4-1 CHECK CRANKCASE OIL LEVEL AND FOLLOW STARTING PROCEDURE
(1) Check the oil level and add or drain oil until to the proper crankcase level.
Low oil or overfilled crankcase oil can cause fuel pump malfunction due to low crankcase
vacuum or a pump restriction due to oil carry over into the pump.
(2) Turn the ignition switch to off, pull 5 or 6 times, then turn switch back to on and start engine
normally.
Following this extra starting procedure on an EFI engine will ensure the cylinder is not
flooded and/or ensure the fuel system has been purged of excess air.
(3) Inspect EFI wire harness for damage. Inspect harness yellow wire with engine temperature
senor closely for damage.
A broken temperature sensor can cause erratic engine performance.
Replace harness as a complete assembly as needed.
(4) While still installed on the engine, inspect throttle body assembly for major damage.
Replace as needed.
5-4-2 INSPECT FUEL PUMP PULSE LINE
(1) Inspect the fuel pump pulse line for any restriction, air leaks or damage Replace as
needed
.
(2) Inspect fuel pump cover on the bottom of the throttle body for cracks or damage. Pay close
attention in the pulse fitting area for cracks.
(3) Inspect throttle body pulse fitting. If throttle body pulse side fitting is loose, repair with green
wicking grade Loctite #290 between fitting and pump cover.
(4)
With the throttle body installed on the engine:
Carefully remove fuel pump pulse line from throttle body pulse pump fitting
Do not damage throttle body when removing the pulse hose
.
Check for excessive oil in the fuel pump pulse hose If excessive oil is found, allow oil to
drain from the pulse line and spray a small amount of carburetor cleaner into the pulse
nipple on the fuel pump
.
After using the carburetor cleaner, blow low air pressure across the pulse nipple to draw out
any oil or carburetor cleaner
DO NOT blow air directly into fuel pump or damage to the throttle body will occur
.
Re-assemble pulse line and re-check engine performance
5-4-3 INSPECT FILTERS AND TANK LINES
(1) Check the air filter Replace as needed
(2)
Inspect the fuel feed pipe for any restriction or damage
Replace as needed
(3)
Check the fuel tank outlet filter as well Replace as needed
(4) Inspect small fuel pump foam filter. Clean or replace as needed.
(5) Inspect fuel injector pressure port cap. If damaged, replace.
(6) Inspect the fuel return pipe for any restriction or damage.
Replace as needed .
(7) Check fuel pump reducer breather hole below throttle body fuel inlet fitting for liquid. If reducer hole
has liquid exiting hole when engine is pulled over or running, replace fuel pump diaphragm assembly.
- 11 -
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6. INSTALLATION
6-1 FUEL SYSTEM
If the fuel tank is detached from the engine, the height from the bottom of the fuel tank to the
fuel joint of the carburetor should be between 5 cm and 50 cm
Any detached tank must have a fuel filter in the fuel feed line with at least 30 micron particle
filtration with a minimum flow rate of 200ml/30 seconds.
The fuel return line must be of at least 3mm inner diameter.
The fuel return line must return to the bottom surface of the fuel tank
An added fuel pump is not needed with the EFI system.
The fuel pump is already integrated into the throttle body assembly
The bottom of the fuel tank can be up to 20 cm below the throttle body
Position the fuel tank carefully because, when it is low, fuel is not fed to the throttle body
When piping the fuel, the hose should be as short as possible and attention should be paid to
heat transmission, size, bending, leakage at hose joints and so on
Care should also be taken to prevent air lock and vapor lock
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7. TROUBLESHOOTING
If the engine shows any sign of malfunction, the cause should be determined immediately
and appropriate countermeasures should be taken to prevent the problem from worsening.
This section describes certain known problems, their possible causes and appropriate
countermeasures. Note, however, that the list of problems presented here is not all. Generally
speaking, since there is the possibility of multiple causes for a single problem, please use your
experience and common sense when deciding on what action to take.
7-1 ENGINE
The following three conditions must be fulfilled for satisfactory engine start.
1. The cylinder filled with a proper fuel-air mixture.
2. Good compression in the cylinder.
3. Good spark, properly timed, to ignite the mixture.
The engine cannot be started unless these three conditions are met. There are also other factors
which make engine start difficult, e.g., a heavy load on the engine when it is about to start at low
speed, and a high back pressure due to a long exhaust pipe.
Problem and possible cause
1. Ignition system problems 1) Spark plug
Remedy
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Adjust the gap
Replace
Clean
2) Ignition coil
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Replace
Repair or replace
3) Improper air gap between ignition coil and flywheel
4) Bad wire harness
Adjust
Replace
Refill
2. Fuel system problems
1) No fuel in fuel tank
2) Fuel hose, Return hose and Fuel pump pulse hose
clogged or pinched
Clean or replace
3) Air in fuel lines
Check and retighten joints
Replace
4) Poor quality gasoline or water in gasoline
5) Throttle body
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Adjust
Overhaul
Check and adjust
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3. Engine core components 1) Insufficient tightening of cylinder head bolts
problems
2) Wearing of piston, piston rings and/or cylinder
Check and retighten
Repair or replace
Repair
3) Improper contact of valve and seat
4) Valve sticking
Repair
5) Improper valve clearance
Adjust
6) Leakage from intake manifold gasket
7) Leakage from carburetor gasket
8) Insufficient tightening of spark plug
Retighten; replace gasket
Retighten; replace gasket
Retighten
- 15 -
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Problem and possible cause
1. Insufficient compression 1) Loosen spark plug
2) Leakage from cylinder head gasket
3) Piston ring seizure or wear
Remedy
Retighten; replace gasket
Retighten; replace gasket
Replace
4) Piston or cylinder wear
Repair or replace
Repair or replace
Repair or replace
Adjust
5) Incorrect valve and seat contact
6) Valve stem seizure
7) Improper valve clearance
2. Ignition system problems 1) Faulty spark plug
2) Faulty ignition coil
Replace
Replace
3) Improper air gap between ignition coil and flywheel
Adjust
4) Demagnetization (flywheel magneto)
5) Bad EFI wire harness
Replace
Replace
3. Fuel system malfunction 1) Throttle body clogged
Inspect, replace
Clean or replace
Check and retighten joints
Replace
2) Fuel strainer and/or hose clogged
3) Air in fuel lines
4) Leaky fuel pump pulse line
5) Poor quality gasoline or water in gasoline
6) Bad EFI wire harness
Replace
Replace
4. Low air intake volume
1. Engine
1) Air cleaner clogged
Clean or replace
Repair or replace
Clean
2) Throttle valve malfunction
1) Cooling air flow obstructed at inlet or cylinder baffle
portion
2) Poor quality engine oil
Replace
3) Lean fuel/air mixture
Check and adjust carburetor
Check and clean or replace
Adjust to rated load
Adjust
4) Excessive back pressure of exhaust system
5) Overloading
1. Trottle body
1) Low idling speed
2. Intake system
1) Air mixing from air intake system joints
Check and tighten;
replace gasket
3. Cylinder head
4. Valve system
1) Gasket faulty (blow-by)
Replace
Adjust
1) Improper valve clearance
2) Leakage from valve seat
Repair
3) Excessive clearance between valve stem and guide
1) Weak spark
Replace
5. Ignition system
Check; adjust or replace
plug
- 16 -
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Problem and possible cause
Remedy
1. Oil leakage
1) Loose oil drain plug
Tighten
Replace
Tighten
Replace
Replace
Replace
Replace
Replace
Replace
2) Faulty oil drain gasket
3) Loose main bearing cover bolts
4) Faulty main bearing cover gasket
5) Crankshaft oil seal (front, rear) defect
1) Faulty piston oil ring
2. Oil up
2) Piston ring seizure, wear or poor contact
3) Excessive wear of piston and/or cylinder
4) Faulty stem seal
5) Excessive oil level
Adjust oil level
6) Breather defect
Repair or replace
Clean or replace
1. Fuel system
1) Clogged air cleaner
2) Faulty throttle body
Repair or replace
Check and repair
2. Engine core components 1) Low compression
2) Overcooling
Check and adjust load and/or
engine speed
1. Ignition system problems 1) Loose ignition system wiring
2) Improper or faulty spark plug
Inspect and tighten
Clean or replace
2. Fuel system problems
1) Lean or rich fuel/air mixture
Clean, adjust or replace throttle
body
2) Throttle body contamination
3) Dirty or clogged fuel lines
Inspect, adjust, or replace
Clean or replace
Tighten; replace gasket
Clean
4) Air mixing from air intake system joints
1) Carbon deposit in combustion chamber
2) Leakage from cylinder head gasket
1) Improper valve clearance
3. Cylinder head
Replace
4. Valve system problems
Adjust
2) Valve heat deterioration
Replace
3) Worn or broken valve spring
4)Improper valve timing
Replace
Adjust
- 17 -
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ENGINE WILL NOT START
Engine does not start
Spark plug improperly
gapped, dirty or fouled
or defective
Clean, regap or replace
as necessary
None or Weak
Check engine
spark
None or Weak
Wiring damaged
Repair of replace
Repair of replace
Replace
Good
None or Weak
Ignition coil - wrong gap
to flywheel or defective
Leaking gaskets at
throttle body or spacer
(insulator)
Possible
Possible
Fuel system
problems
Poor fuel quality or water
in system
Flush and/or refill
Clean or replace
Hoses for fuel supply, return
or pump pulse restricted
or leaking
Possible
Possible
Throttle body clogged or
damaged
Clean or replace
None
Loose spark plug
Loose head bolts
Tighten
Compression or
core component
problems
Retorque
Replace
Leaking at cylinder head
Bad head gasket
Worn piston, rings or
cylinder head
Repair
Check or reset
valve clearances
Leaking at valves
Improper contact
at valve and seat
Repair
Repair
Valve stuck in
guide
Check for condition of cam,
chain and rockers
Repair as required
-18
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8. MAINTENANCE AND STORAGE
The maintenance jobs described below apply to correct use of the engine under normal
conditions.
The maintenance intervals mentioned in this section are not a guarantee that no maintenance is
required during those intervals.
For example, when the engine is used in dusty conditions, the air cleaner should be cleaned every
day, rather than every 100 hours.
8-1 DAILY MAINTENANCE (EVERY 8 HOURS OF USE)
MAINTENACE ITEMS
(1) Clean dust from engine.
REASON / REMARKS
(1) Dust can impair operation of various parts.
Governor linkage is especially sensitive to dust.
(2) Uneconomical and dangerous.
(2) Check for fuel leakage. Tighten or replace parts,
if necessary.
(3) Looseness can result in vibration and accidents.
(3) Check all parts are securely fastened. Tighten,
if necessary.
(4) Check oil level and add up to full mark.
(4) Running the engine with insufficient oil can result in
serious problems, including engine seizure.
(5) Check that the air cleaner element is clean.
Clean or replace, if necessary.
(5) A clogged air cleaner can cause power loss and
malfunction.
8-2 INSPECTION AND MAINTENANCE AFTER THE FIRST 20 HOURS
MAINTENACE ITEMS
REASON / REMARKS
(1) Change the crankcase oil.
(1) Sludge is deposited during running-in.
8-3 INSPECTION AND MAINTENANCE EVERY 100 HOURS (EVERY 10 DAYS)
MAINTENACE ITEMS
REASON / REMARKS
(1) Change the crankcase oil.
(2) Clean the air cleaner and fuel tank outlet filter.
(1) Contaminated oil quickens wear.
(2) A clogged air cleaner and fuel filter can cause engine
malfunction.
(3) Inspect the spark plug. Clean with gasoline or polish (3) A faulty spark plug can cause low power output and
with sandpaper if dirty. poor starting performance.
8-4 INSPECTION AND MAINTENANCE EVERY 100 TO 200 HOURS (EVERY MONTH)
MAINTENACE ITEMS
REASON / REMARKS
(1) Clean the fuel strainer and fuel tank.
(1) Contaminated fuel can cause engine malfunction.
(2) Change the air cleaner element and fuel tank filter.
(2) A clogged air cleaner and fuel filter can cause engine
malfunction.
- 19 -
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8-5 INSPECTION AND MAINTENANCE EVERY 300 HOURS
MAINTENACE ITEMS
REASON / REMARKS
(1) Inspect the intake and exhaust valve clearance.
Adjust if necessary.
(1) Incorrect clearance can cause low power output
and engine malfunction.
8-6 INSPECTION AND MAINTENANCE EVERY 500 TO 600 HOURS (EVERY 6 MONTHS)
MAINTENACE ITEMS
REASON / REMARKS
(1) Remove the cylinder head and remove any carbon.
(2) Disassemble and clean the carburetor.
(1) Carbon deposits can cause engine malfunction.
(2) A faulty carburetor can cause engine malfunction.
8-7 MAINTENANCE EVERY 1,000 HOURS (ANNUAL MAINTENANCE)
MAINTENACE ITEMS
REASON / REMARKS
(1) Overhaul the engine. Clean and correct the engine
parts, replacing if necessary.
(1) Dirty, misaligned or worn parts can cause low power
output and engine malfunction.
(2) Replace the piston rings.
(2) Faulty piston rings can cause low output power and
engine malfunction.
(3) Replace the fuel hose.
(3) To prevent fuel leakage and attendant dangers.
8-8 ENGINE STORAGE
(1) Carry out the maintenance jobs described in step 8-1 above.
(2) Drain fuel from the fuel tank and carburetor float chamber.
(3) To prevent rust in the cylinder bore, inject oil through the spark plug hole, pull the recoil starter
knob gently 2 or 3 times and then put back the spark plug.
(4) Pull the recoil starter knob until the resistance is heavy. Leave it in that position.
(5) Clean the exterior of the engine with an oiled cloth. Place a plastic cover or similar over the
engine, and store the engine in a dry place.
- 20 -
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9. ORGANIZE
Most people know that engines will require daily and periodic maintenance, but it’s also important
to be aware of the audible and visual signs of unexpected maintenance needs. Operators should
also take into consideration working conditions and how they affect engine performance. Proper
engine storage shouldn’t be overlooked either.
Addressing the small issues early on, making appropriate environmental adjustments and
following storage guidelines will all help prevent engine troubles from creeping up in the future.
9-1 TROUBLESHOOTING
If an engine is experiencing hard starts, check the oil level and add or drain oil until to the proper
crankcase level. Turn the ignition switch to off, pull 5 or 6 times, then turn switch back to on and start
engine normally. Following this extra starting procedure on an EFI engine will ensure the cylinder is not
flooded and/or ensure the fuel system has been purged of excess air.
If an engine is still experiencing hard starts, the valve clearance on the intake and exhaust valves
should be checked and adjusted according to manufacturer specifications. When checking the valve
clearance, position the piston at the top dead center of the compression stroke and ensure the engine
is cold. After the clearance is adjusted, rotate the crankshaft and check the valve clearance again.
A reduction in power often is an indication that the fuel tank outlet filter and/or cylinder head needs to
be inspected and cleaned. Check the oil level and add or drain the oil until to the proper level. Check
the air filter and fuel tank outlet filter as well. Check the fuel pump pulse line for any restriction, air leaks
or damage. Replace as needed. Check the cylinder head’s valves, seats, ports and guides and remove
any carbon or gum deposits from the components.
If the recoil rope hangs loose and doesn’t completely return, it could be a sign that water has intruded
the engine. This indicates the lubricant may have been washed off. Remove the recoil return and apply
additional lubrication to fix the problem. Ignoring the issue can result in a broken rope or eventual
damage to the recoil starter.
Additionally, a loss of power or a smoking engine may signal an internal engine problem. Blue-colored
smoke indicates that the engine is using oil, a problem that tends to be more common on cold days.
Look to see if the breather hoses are plugged and check the piston rings, which may be bad, to
determine the cause of the smoke.
If the smoke is black in color, it typically indicates that the mixture is too rich. Incorrect mixtures of air
and fuel cause the majority of throttle body problems; therefore, it is important to prevent clogged air
passages and fuel passages that keep air and fuel from flowing freely. Check the throttle body for dirty
or defective parts and clean or replace the entire throttle body assembly if needed. Check the throttle
body fuel feed and return lines for any restriction or damage. Replace as needed. A change in elevation
also may cause black smoke, in which case the engine should be modified to handle the difference.
If basic troubleshooting maintenance techniques fail to work, have a trained mechanic conduct a
leakdown test or compression test to determine the cause for any smoking or power reduction.
Like smoke colors, different noises also can indicate specific problems. For instance, if the engine
begins to make a popping noise or backfire, the mixture of fuel and air is likely too lean in the throttle
body. A knocking noise will generally indicate a worn connecting rod, while a tinny or metallic sound
may mean something is loose.
- 21 -
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9-2 ADJUSTING FOR THE ENVIRONMENT
In addition to a regular maintenance routine, some application circumstances require special care,
such as high altitudes, heat and cold.
Altitudes above 5,000 feet may cause engines to start hard and perform poorly. Emissions also
are typically higher, and operators may experience trouble with spark plugs. Modifying the throttle
body can improve both performance and emission levels. Moving to a job site below 5,000 feet
requires converting the engine back to levels recommended by the manufacturer. Failure to do so
will cause the engine to overheat and can result in damage.
Operating an engine after the mercury has surpassed 100 degrees Fahrenheit also can be
problematic. Ensuring dirt does not obstruct an engine’s cooling mechanisms will help prevent
problems with overheating. However, do not attempt to cool a hot engine with water since the
temperature difference will likely damage the engine.
Operators also should check and change the oil and oil filter more frequently than normal when
using an engine in hot weather. Take the heat into account when choosing the oil’s viscosity, as
well.
On the other end of the thermometer, monitoring the oil’s viscosity remains important. If a cold
front should move in before the oil has been changed to a more appropriate viscosity, move the
machine to a warm, well-ventilated space before attempting to start the engine or change the oil.
Keeping the fuel tank full will prevent moisture from condensing inside the tank when it’s cold,
which can cause problems with engine operation. Ensuring the battery remains well-charged also
will combat problems an operator may face in a cold environment.
One trick to ease frustration if the machine needs to remain outside and an ice storm is
anticipated is to push the throttle to the middle of its speed range. Should ice form on the linkage,
it will be easier to start the engine with the throttle in this position.
- 22 -
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9-3 SUITING UP FOR STORAGE
Whether it’s the off-season or other circumstances prevent operating your engine-powered
equipment for more than 30 days, special steps need to be taken to protect the engine.
The first step in preparing an engine for storage is performing all of the suggested daily
maintenance items, such as cleaning the engine and checking the air filter. Next, run the engine
completely out of fuel or drain the fuel from the fuel tank . This is one of the most important steps
in preparing an engine for storage. Over time the volatile components of fuel evaporate and the
fuel becomes stale. Stale fuel makes starting the engine difficult, if not impossible, when the
machine is taken out of storage. Although it is usually suggested to drain the fuel, filling the tank
with new fuel and adding a fuel stabilizer is another option for preventing a stale situation.
To prevent corrosion in the cylinder bore during storage, remove the spark plug and inject a few
drops of oil through the spark plug hole. Gently pull the recoil starter knob two or three times
before the spark plug is placed back in the spark plug hole. Additionally, pull the recoil starter knob
until the resistance is felt, and leave it in that position. End the process with a final engine cleaning
before placing a protective cover over the unit and storing it in a dry place.
When returning the engine to service, ensure the oil viscosity is adequate for the temperatures
expected. Check the fuel lines and filter, making sure they are still secure and have not cracked.
Be sure that the throttle, choke and governor linkages move freely before starting the engine.
The initial start for an engine coming out of storage may be slow and there could be smoke for a
few minutes until any oil in the cylinder burns off. If the engine fails to start, check the spark plug
since it may have been fouled by the oil added to the cylinder before the machine was stored.
Clean or replace the spark plug before attempting to start the engine again.
Whether you’re preparing an engine for storage, adapting it to the weather or just keeping an eye
out for warning signs, giving an engine the attention it deserves will go a long way toward keeping
it out of trouble.
- 23 -
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