2003 KING
Owners / Service Manual
“CHAMPIONS START HERE”
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DISCLAIMER OF WARRANTY
This motorcycle is sold “as is” with all faults, obvious or not. There are no warranties
expressed or implied, including any warranty of merchantability and warranty of fitness
for any particular purpose.
“WARNING”
THE COBRA KING IS A COMPETITION MODEL ONLY AND IS NOT
MANUFACTURED FOR, NOR SHOULD IT BE USEDON PUBLIC STREETS, ROADS
OR HIGHWAYS.
THE USE OF THIS BIKE SHOULD BE LIMITED TO PARTICIPATION IN
SANCTIONED COMPETITION EVENTS UPON A CLOSED COURSE BY A
SUFFICIENTLY SKILLED RIDER AND SHOULD NOT BE USED FOR GENERAL
OFF-ROAD RECREATIONAL RIDING.
IMPROPER USE OF THIS MOTORCYCLE CAN CAUSE INJURY OR DEATH.
THIS BIKE IS INTENDED FOR EXPERIENCED RACERS ONLY AND NOT FOR
BEGINNERS.
IT IS YOUR RESPONSIBILITY AS THE OWNER OF THIS COBRA MOTORCYCLE
OR AS THE PARENT, OR LEGAL GUARDIAN OF THE OPERATOR, TO KEEP THIS
COBRA MOTORCYCLE IN PROPER OPERATING CONDITION.
THIS BIKE WAS DESIGNED FOR RIDERS THAT WEIGH LESS THAN 80 LBS WITH
FULL RIDING GEAR AND SHOULD NOT BE OPERATED BY RIDERS THAT WEIGH
MORE THAT.
BE SURE THAT THE RIDER ALWAYS WEARS ADEQUATE SAFETY GEAR
EVERYTIME HE OR SHE RIDES THEIR COBRA MOTORCYCLE.
IMPORTANT SAFETY NOTICE
Failure to follow WARNING instructions could result in severe injury or death to
the machine operator, a bystander, or a person inspecting or repairing the
machine.
CAUTION:
A CAUTION indicates special precautions that must be taken to avoid damage to
the machine.
NOTE:
A NOTE provides key information to make procedures easier or clearer.
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Table Of Contents
General Information .........................................................................................................4
Specifications - General..............................................................................................4
Optional Components..................................................................................................5
Specifications - Torque Values ..................................................................................6
Break-In Procedure......................................................................................................7
Starting Procedure .......................................................................................................8
General Tips..................................................................................................................9
Maintenance......................................................................................................................9
Schedule & Tips ...........................................................................................................9
M1: Replacing Transmission / Clutch Lubricant....................................................10
M2: Chain adjustment................................................................................................12
M3: Rear brake adjustment ......................................................................................12
M4: Air Filter Cleaning ...............................................................................................13
M5: Fork Oil Replacement........................................................................................13
Engine Service / Parts ...................................................................................................15
ES1: Engine Service..................................................................................................17
E1: Engine Removal..............................................................................................18
E2: Complete Engine Disassembly Procedure .................................................19
E3: Top End Disassembly Procedure.................................................................19
E4: Splitting the Cases..........................................................................................20
E5: Engine assembly.............................................................................................21
ES3: Clutch.................................................................................................................26
ES4: Ignition................................................................................................................30
ES5: Cooling System.................................................................................................32
ES6: Fuel & Air System.............................................................................................36
ES7: Exhaust ..............................................................................................................39
Chassis Service / Parts .................................................................................................40
CS1: Wheels & Tires .................................................................................................40
CS2: Suspension........................................................................................................47
Troubleshooting ..............................................................................................................50
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General Information
Specifications - General
Items
KING
Dimensions
Wheelbase
Wheel size
Seat height
Engine
39” (991mm)
10” (254mm) rear, 12” (305mm) front
26” (660mm)
Type
2-stroke, single cylinder, reed valve
Liquid-cooled
Cooling system
Displacement
Bore and stroke
Ignition system
Spark plug
49.8 cc
39 mm x 41.7 mm
Electronic
Splitfire SF406B
Gap 0.023” – 0.025” (0.58 – 0.64 mm)
0.050” (1.3 mm) Before To Dead Center (BTDC)
Sunoco MO2X or 93 octane pump gasoline
OTHER RACE FUELS ARE NOT RECOMMENDED
Cobra Venom 2-cycle Race Oil
Between 32:1 and 40:1 (after engine Break-In is
complete)
Ignition timing
Fuel type
Oil type
Fuel / oil mix ratios
Carburetion
19 mm Dell’Orto
Main Jet 94
Slow (Pilot) jet 65
Float Height 16mm + 0.5mm (0.63” + 0.020”
Transmission
Speed
Single
Clutch
Cobra 3 shoe
13/39 T
Final drive ratio
Chain
100 links 420
Transmission / clutch oil type
Cobra Venom 3 Shoe Clutch Milk, or Dexron III
Quantity 235 ml (8.0oz)
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Chassis
Front tire
2.50 - 12
Pressure 15 psi minimum
2.75 - 10
Rear tire
Pressure 15 psi min. (20 psi for hard pack or rocky conditions)
Cobra 30mm USD
Front fork
Fork oil type SAE 5 weight
Fork oil amount 118 ml (4.0 oz)
Optional Components
·
·
Carburetor jets
Sprockets
o Front
o Rear
·
·
·
Suspension Springs
Weight of Rider (lb)
Less than 51
Fork Spring
Shock Spring
7 lb/in,
KCKG0007
9 lb/in,
KCKG0009
12 lb/in,
KCKG1200
SCKGOH10 (yellow, 175lb/in)
51 - 60
SCKGOH85 (gray, 185 lb/in)
SCKG0H, (white, 195 lb/in)
Greater than 60
Suspension Valving
Damping Rate
Fork Valving
Compression
Fork Valving Shock Valving
Rebound
(mid valve)
(kit)
(base valve)
Soft (fast)
Standard
KAKG0013
KAKG0016
KAKG0017
KAKG0018
SCKGOH24A
SCKGOH24
SCKGOH24B
KAKG0014
KAKG0015
Hard (slow)
Cobra BIG AIR SX Fork Kit part #KKKG2003
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Specifications - Torque Values
Torque Value
Size &
Remarks
¼”
Fastener
Cylinder head nuts
Crankcase bolts
Spark plug
ft-lb
9.2
6.6
(SP)
2.1
1.7
5.8
40
in-lb
110
80
Nm
12
9
6 x 1.0
14 x 1.25
#8
(SP)
25
(SP)
2.8
2.3
7.9
54
Stator bolts
Stator cover bolts
Clutch cover bolts
Clutch
20
#8
70
6 mm
10***
480
300
Front axle nut
25
34
12 x 1.25
Front brake caliper
Engine mount bolts
Swingarm Pivot
Intake manifold bolts
Rear Axle Bolt
Rear Sprocket Bolts
Fork cartridge rod
Triple clamp bolts
Fork cap
22
21
4.6
25
18
12
6
265
250
55
30
28
6.2
34
24
16
8
8 mm
14 mm
6 mm
300
216
144
72
12 mm
7 mm
6 x 1.0
1.25” x 18
10 mm**
5
60
6.7
54
Ignition rotor nut
40
480
** Use green (wicking / bearing retainer) thread locker, with primer, on the
flywheel / crankshaft taper but none on the threads.
*** Use green (wicking / bearing retainer) thread locker, with primer, on the
crankshaft / clutch taper but use red (high strength) thread locker, with primer, on
the nut.
(SP) To apply the proper torque to the spark plug when inserting, one must first
screw the spark plug in until the metal gasket ring causes resistance and then
turn another 1/8 to ¼ turn.
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Break-In Procedure
Your Cobra KING is a close-tolerance high performance machine and break-in
time is very important for maximum life and performance. The KING can be
ridden hard after the first ½ hour break-in time but it is recommended that no
adjustments are made to the carburetion or suspension until the full 8 hours of
bike break-in has elapsed. Also, after the engine, transmission, and drive train
have been broken-in for the full 8 hours, the bike will be faster!
Use a fuel / oil mixture of 32:1 for the full 8 hour break-in period. Be sure to use
93 octane pump gas, or Sunoco MO2X , with Cobra’s specially formulated Cobra
Venom 2-cycle Race Oil. (Part # MCMUOL02)
CAUTION:
Failure to use proper fuel, oil, or fuel/oil mixture may result in premature engine
wear or damage to the machine.
Adhering to the following break-in schedule will result in long lasting high
performance machine.
·
·
First ½ hour of operation
o
o
Follow the starting procedure listed in this manual.
Avoid prolonged operation at Wide Open Throttle.
After 1 hour of operation
o
Check for loose bolts and nuts on the bike and retighten as
necessary (proper toque values are listed under Specifications).
o
o
Clean the carburetor bowl.
Change the transmission / clutch lubricant.
·
·
After 8 hours of operation
o
o
Change the fork oil.
Have a Certified Cobra Mechanic change the shock oil.
Your bike is now ready for the highest level of competition!
NOTE:
During break-in the bike will likely loose some engine coolant through the radiator
overflow hose. Loosing up to 4 oz (120 ml, ½ cup) is normal. Proper coolant level
will cover the top of the radiator cores. Removing the radiator cap and looking
inside is the only way to check the coolant level.
Never open the radiator cap of a machine that has a hot or warm engine or one
that has recently been ridden. Burning and scalding could occur.
CAUTION:
It is important that the radiator cap is installed correctly and completely otherwise
engine damage could occur.
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Starting Procedure
Before starting the machine inspect the following:
·
·
·
·
·
Check for proper tire pressure in both tires.
Observe the chain tension and adjust if necessary.
Observe the coolant level and fill if necessary.
Verify that the chain rollers do not have improper wear.
Inspect the frame, for;
o
Cracks in the metal.
o
Cracking paint which might indicate overly stressed material.
·
·
Verify that the handlebars are tight.
Check the throttle for;
o
o
Smooth operation and sound closing.
Frayed strands of the cable inside the throttle housing.
·
·
·
Check for loose bolts and nuts, and re-torque as necessary.
Verify that the air filter is clean and properly saturated with oil.
Insure that the fuel tank contains an adequate volume of fuel / oil mixture to
complete the distance required. (Sunoco MO2X or 93 octane pump gas with
Cobra’s specially formulated Cobra Venom 2-cycle Race Oil)
Turn the fuel on by rotating the fuel petcock knob to the vertically downward
position (reserve position is horizontally forward)
·
CAUTION:
For best results from your Cobra Motorcycle use only the recommended fuels.
Testing has shown that most ‘race’ fuels actually degrade performance.
When your pre-ride inspection is complete the bike may be started. For a cold
engine follow this procedure.
1. Place the motorcycle on a stand of sufficient strength that positions the
motorcycle in a level upright position with the rear wheel off the ground.
2. Pull up the choke knob and turn it to lock it.
3. Kick start the engine.
4. Rev the engine in short spurts, turning the throttle no more than 1/4 open
until the engine will run without the choke.
5. Verify a functional engine shut-off switch by shutting off the engine.
6. Restart the engine and proceed with riding when the engine is sufficiently
warm (i.e. the side of the cylinder is warm to touch).
CAUTION:
Never rev an engine full throttle when it's cold or slightly warmed up. Cobra
recommends that you tell your child to take it easy the first couple of minutes in
practice until the engine comes up to full operating temperature. Make sure your
engine is properly warmed up before racing.
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General Tips
1.
2.
Always wear a helmet and other protective riding gear.
Cobra recommends that you tell your child to take it easy the first couple of
minutes in practice until the engine comes up to full operating temperature.
Make sure your riders’ foot is not resting on the foot brake while they are
riding.
3.
4.
Evaluate the bikes jetting only after it has been warmed up to race
temperatures.
5.
6.
A properly maintained machine is safer, faster, and more fun to ride.
Your Cobra Motorcycle has a 10 digit VIN (Vehicle Identification Number).
The first two digits indicate the model and the seventh indicates the model
year (MY).
a. Example, ACxxxx3xxx is a 2003 MY King.
Maintenance
Schedule & Tips
It is important that you adhere to this maintenance schedule so as to promote the
longevity of your Cobra Motorcycle.
·
Between each ride
o
o
Check the air filter (clean and re-oil as necessary).
Insure the smooth operation of the throttle cable (throttle soundly
‘clacks’ shut).
o
Check for frayed strands of the throttle cable inside the throttle housing
and replace if necessary.
o
o
o
o
Check for adequate tire pressures and adjust if necessary.
Check all nuts and bolts for proper torque and re-torque if necessary.
Spray all moving parts with WD40 or other light oil.
Check drive chain for
§
Proper tension and adjust if necessary.
§
Adequate lubrication and lubricate if necessary.
o
o
Insure that the ignition stator and rotor are clean and dry.
Check the frame for cracks in the metal or cracks in the paint that
might indicate that the metal has been stressed beyond it’s safe limits.
Replace or get properly rewelded as necessary.
o
Inspect the rear sprocket damper plate for bending or warping.
Straighten or replace if more than 1/16” (1.6 mm) from flat.
·
·
Every 2 hours of operation
Replace the transmission oil.
Every 10 hours of operation
o
o
o
Replace the fork oil.
Have the shock oil replaced by a Certified Cobra Mechanic.
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CAUTION:
1.
Because of the amount of heat generated by the clutch and engine during
extended periods of riding, it is advisable to remove the ignition cover
afterward to allow the ignition to cool off. The heat transfers through the
cases and can damage the stator as it cools off because of lack of airflow
around the stator.
2.
If you ever need to weld anything on the bike, disconnect the spark plug
cap, unplug the ignition, disconnect the kill switch, scrape the paint bare
near the area to be welded and put the ground clamp as close to the area
to be welded as possible.
Be sure the fuel tank and carburetor have been removed and safely located
away from the welding process.
3.
The frame is 4130 Chrome Moly and it is important to weld it with the proper
rod and heat settings set as light as possible. Cobra recommends replacing
the frame with a new one if the old one becomes damaged.
4.
If your kick-starter lever does not return to the rubber bumper, use WD-40
or light penetrating oil under the plastic cover behind the spring on the
shaft. The shaft is a very close fit to the case and also has an O ring in it
and is difficult to get lubrication to which may cause binding. If it does not
loosen up, remove the kick-starter cover and kicking assembly. Grease the
shaft.
M1: Replacing Transmission / Clutch
Lubricant
Tools needed:
·
225 ml (7.6 oz) Cobra Venom 3 Shoe Clutch Milk (Part # MCMUGF01), or
Dexron III Automatic Transmission Fluid.
·
13 mm combination wrench
Procedure:
1. Begin this procedure with a bike that has been ridden more than 5 minutes
but less than 10 minutes. It is desired to have the engine warm enough so
that the oil ‘runny’ but not so hot that there is risk of being burned by the
engine or the oil.
Hot oil and hot components on the motorcycle may cause burns.
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2. Lean bike against something or set on stand with oil drain hole.
3. Using a 13 mm wrench, remove the oil drain bolt located on the right side of
the engine, on the clutch cover, near the brake lever (Item 2, figure 1).
Figure 1
NOTE: You may need to adjust the brake pedal (up or down) to gain access to
the drain bolt.
4. After it has drained, reinstall the bolt being sure that the copper gasket is in
place. Torque to 15 Nm (11 ft-lb).
5. Reapply oil from oil fill plug 235 cc Cobra Venom 3 Shoe Clutch Milk, or
Dexron III Automatic Transmission Fluid, thru the fill plug.
NOTE lean bike over onto it’s left hand side so that the clutch cover is up unless
you have a squeeze bottle.
6. Reapply the oil fill bolt, hand tight, being sure the fiber gasket is in place.
CAUTION:
Cobra has spent considerable time and money developing the proper lubrication
to handle the harsh environment of the automatic clutch and transmission of this
motorcycle. Cobra was forced to put forth this effort because the other available
options and not adequate. Cobra’s specially developed Cobra Venom 3 Shoe
Clutch Milk (Part # MCMUGF01) is the recommended lubricant for your KING
motorcycle.
11
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M2: Chain adjustment
1. Make sure that the rear
wheel is aligned properly.
2. Push down on the seat,
compressing the suspen-
sion down to where the
chain is tightest.
3. The chain should not be
too tight but not too
loose. A minimum of 2.5
in. of slack should be
between the swing arm
and the chain.
Figure 2
M3: Rear brake adjustment
Tools recommended for rear brake maintenance:
10mm open end wrench
There are 2 adjustments on the brake.
Figure 3, adjust brake lever free height
Figure 4, adjust brake lever ‘free play’
From the brake lever:
1. Loosen the 10mm nut on the back of the brake pedal.
2. Adjust the bolt to desirable position
3. Tighten the 10mm nut.
From the brake hub:
1. Adjust the wing nut up to desirable position.
CAUTION:
If you tighten the wing nut up too much, the brakes may hang up. If so, the brake
pads will burn up, and need replaced.
12
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M4: Air Filter Cleaning
Tools recommended for air filter maintenance:
·
·
·
·
Flat head screwdriver
Air filter oil
5mm hex key
Foam filter oil
The Cobra is equipped with a special designed sock filter. It is very important to
keep it clean and properly oiled with high quality water-resistant foam filter oil.
It’s very important to oil your filter consistently each time because varied amounts
of oil will change your carburetor jetting.
Make sure you change your filter after each moto. We recommend carrying 3 or
more filters in your toolbox.
1 for practice
1 for the each moto
In our testing when filters are properly oiled, no water, dirt or mud can penetrate
through the yellow or red foam to the carburetor inlet. It is important that the filter
does not touch any of the frame components in a rainy, muddy situation. We
offer two different filters. One filter for the use in sand (part # RCMU0101), and
the regular filter for regular use (part # RCMU0206).
When washing your bike cover the carburetor/filter with a suitable shield capable
of keeping water from entering the engine. Cobra has a rubber clamp-on plug for
the carburetor referred to as a carburetor condom (part # RCMU0104).
M5: Fork Oil Replacement
Tools required
·
·
·
·
Two 19 mm wrenches or sockets
4 & 5 mm hex key (Allen wrench)
1 1/8” wrench or socket
5 wt fork oil
Disassembly procedure
1. Remove the front wheel (19 mm wrench).
2. Remove the brake caliber from the fork leg (4 mm hex key).
3. Loosen the fork caps (1 1/8” socket).
4. Remove the fork legs from the triple clamps (5 mm hex key).
5. One leg at a time
a. Remove the fork cap from the leg.
b. Separate the fork cap from the damper rod.
c. Pull out the fork spring.
d. Place upside down over a suitable pan, tray, or container.
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e. Work the damper rod up and down several times.
f. Allow to drain completely.
Assembly procedure
1. Fill the fork leg with 4 oz (118 ml) 5 wt fork oil.
2. Measure the fork oil level to the top of the fork tube with the leg collapsed,
and record for tuning purposes.
3. Install the fork spring.
4. Reconnect the damper rod to the fork cap (12 ft-lb, 16 Nm).
CAUTION:
The damper rod is hollow and will break if the nut is over tightened.
5. Reinstall the for cap into the fork leg (5 ft-lb, 6.7 Nm)
6. Reinstall the fork legs into the clamps (6 ft-lb, 8 Nm).
7. Reinstall the brake caliper.
8. Reinstall the front wheel (25 ft-lb, 34 Nm).
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Engine Service / Parts
2003 KING ENGINE ASSEMBLY REFERENCE DRAWING
REF. # PART #
DESCRIPTION
REF. # PART #
DESCRIPTION
1
2
3
4
5
6
7
8
9
CAKG0002 Clutch, Complete
44 ZCKG0002 Gasket, Base
45 ECKG0041 Cylinder, 50cc
46 ZCMUOR07 Oring, Exhaust Flange
47 ECKG0015 Exhaust Flange
48 HCBC0602 Screw, 6x20
CAKG0004 Shoes, Clutch w/ Washer Springs
CAMU0008 Spring Set, Washer type for Clutch
CCMU0031 Arbor for 3 Shoe Clutch
ECMU0018 Nut, Crankshaft Starter
ECMU0033 Clutch Hub w/ Gear
ECMU0040 Clutch to hub spacer
ECDC0105 90 Degree Crankcase Vent
ECMU0017 Seal, Crankshaft
49 ECMU0008 Stud, Cylinder
50 ZCMUOR03 Oring, Cylinder head, Small
51 ZCMUOR05 Oring, Cylinder head, Medium
52 ECKG0121 Cylinder Head Dome-Insert
53 ECMU0403 Spring, Kickstarter Return
54 HCNS1401 Nut, 1/4-20
55 ZCMUOR02 Oring, Cylinder head, Large
56 ZCMUOR08 Oring, Cylinder head
56A ZAKGOR02 Oring Kit, Top End
57 ECKG0025 Cylinder Head - Outer Cap
58 HCWF1401 Washer, 1/4"
10 ECMU0016 Bearing, Crankshaft
11 ECMU0001 Bearing, Trans., Secondary Gear
12 ECMU0020 Bearing, Trans., Precision
13 ECMU0105 Gear, Trans., Primary
14 HCNS1202 Nut, 1/2-20, Left Hand
15 ECKG0018 Crankcase, Clutch side
16 ECMU0131 Water Elbow
17 HCBH0805 Screw, M8x12mm
18 ECMU0103 Shaft, Trans., Secondary w/gear
19 ECMU0104 Shaft, Trans., Output w/gear
20 ECKGBR01 Bearing, Trans., Output shaft
21 ZCKG2001 Gasket, Crankcase
22 HCDP1401 Dowel, for Engine Cases
23 ECMU0038 Crankshaft, Welded and Balanced
24 ECKG0017 Crankcase, Ignition side
25 ECKG0004 Snap Ring, Int. for Water Pump
26 ECKGSE01 Seal, Output shaft
27 HCBC0606 Screw, M6x45
59 ICMU0006 Rotor
60 ICMU0007 Stator
60A MCKGGR00 Grommet, Engine case
61 ECKG0073 Impeller, Waterpump
62 ECKG0074 Seal, Waterpump
63 ECKG0203 Intake Manifold
64 ZCMU0032 Gasket, Reed to case
65 ZCMU0031 Gasket, Intake to Reed
66 ECKG0202 Reed Assembly
66A ECKG0204 Reed Kit
67 ZCKG0101 Gasket, Ignition Cover
28 HCBC0604 Screw, M6x35
68 ECKG0001 Cover, Ignition
28A HCBC0603 Screw, M6x30
29 HCBC0608 Screw, M6x55
69 HCBC0802 Screw, 8-32x1-3/4
70 ECMU0043 Piston Kit
30 PCKG0013 Sprocket, 13T for output shaft
30A ECKGSR03 Snap Ring, Ext., for output shaft
31 HCWP0001 Washer, Stator
32 HCBH0803 Screw, 8-32x7/8
33 HCBC0801 Screw, 8-32x1-1/2
34 HCNS1001 Nut, 10mm
35 ECKG0042 Pulley, Waterpump-Crank
36 ECKG0070 Belt, Waterpump
37 HCBB0001 Screw, 10-32x1/2"
37A HCBC1033 Screw, 10-32x3/4"
38 HCWL0001 Washer
39 ECMU0080 Belt Retainer
40 ECKG0075 Pulley, Waterpump-Fan
41 HCSS8201 Screw, 8-32x3/8
70A ECMU0055 Piston Ring
71 ECKG0012 Wrist pin
72 ECMU0077 Bearing, Wrist Pin
73 ECMUSR00 Snap Ring for Piston
74 ECMUSP01 Spring, Kick Start Dog
75 ECMU0207 Gear, Kickstarter, Small
76 ZCMU0030 Gasket, Clutch Cover
77 ECMU0205 Kick Starter Rubber
78 HCWC0000 Gasket, Copper
79 HCBH0805 Screw, M8x12mm
80 ECMU0204 Kick Starter Dust Shield
81 ZCMU0001 Gasket, Oil fill plug
82 ECMU0037 Oil fill plug
83 ECMU0202 Kickstarter Lever
84 ECMU0027 Kickstarter, complete
85 ECMU0003 Brass Clutch Bushing
42 ECKG0072 Bearing, Waterpump
43 ECKG0141 Shaft, Waterpump
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Figure 5
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Trained technicians with precision gauging and proper assembly fixtures carefully
assemble all Cobra engines to specific clearances. If you feel you have the skills,
and the appropriate tools, to perform the following service tasks please follow the
instructions closely. The part numbers are listed throughout to help you when
ordering parts from your local Cobra dealer.
If you don’t feel comfortable with the service work, simply take your engine out of
the frame and sent it to:
Cobra Precision Engines
11511 Springfield Road
North Lima, Ohio 44452
Cobra has specialized mechanics that will go through the entire engine, replacing
gaskets, bolts, any old part that is worn. The engine will be rebuilt using the
same precision gauging and assembly fixtures as when it was assembled new.
Before leaving, the engines performance will be measured on a dynamometer to
ensure that your engine is operating at its highest potential. All this for one low
nominal fee. Call (330) 549-9603 for details.
ES1: Engine Service
One method for determining whether the top end of your engine needs rebuilt is
to perform a WOT (Wide Open Throttle) kicking compression test. Before
performing the procedure please read the caution notes below.
CAUTION:
·
·
·
There appears to be a wide range of variability in reading compression
gauges across the country.
The head volume of this Cobra Motorcycle is very small and so requires many
kicks ~20 before you establish the most accurate reading possible.
Because of the geometry of the spark plug used in this Cobra Motorcycle, the
adapter used with your compression tester must have a similar volume
protruding into the combustion chamber to establish an accurate value.
·
Length of hose on the compression tester will affect the reading. The shorter
the hose length the more accurate your reading will be.
Because of these difficulties in measuring an absolute compression value, a
useful relative value can be achieved by testing your bike’s compression with
your own particular gauge after a new top end or when the bike is new so that
you know what your particular gauge reads on a ‘fresh’ engine. When it has
dropped to 90% of its original value the engine will be down on power and would
benefit from a rebuild. When it’s dropped to 80% it really needs rebuilt! Using the
table below will help you determine monitor the condition of your top end.
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Engine is Fresh Engine Down on Power Engine NEEDS Rebuilt
Measured Value
Measured Value * 0.9
Measured Value * 0.8
110 psi
110 psi * 0.9 = 99 psi
110 psi * 0.8 = 88 psi
Example
Your Values
Procedure for Compression Testing
1. Shut off the fuel petcock.
2. Install the compression gauge into the spark plug hole.
3. Hold the throttle to wide open, and kick repeatedly (approximately 20 times)
or until the gauge reading does not increase in value with each kick.
E1: Engine Removal
To service the bottom end and transmission, the engine must be removed from
the frame.
Tools required
·
·
·
·
·
·
·
·
5/16”, 10, 14, 22 mm socket
10, 13, 22 mm wrench
10, 17 & 19 mm sockets
9/64”, 3,4 & 5 mm hex key (Allen wrench)
7 mm nut driver, flat or Phillip, screwdriver for hose clamps
Spring remover
Flywheel / clutch puller (#MCMUTL68)
Clutch nut removal tool (Call local dealer for details).
Procedure
1. Remove the seat (4mm hex key).
2. Turn of the fuel at the petcock and disconnect the fuel line.
3. Remove the tank (5 mm hex key & 10 mm socket).
4. Remove the carburetor from the inlet (flat head or Phillips head screwdriver, 7
mm nut driver).
5. Remove the right side number plate (3mm hex key).
6. Remove the silencer & pipe (spring remover, 5mm hex, & 10mm wrench).
7. Disconnect the ground wire from the reed cage with a 5 mm hex key
(depending on your ultimate repair, you may want to reinstall the fastener in
the inlet.
8. Leaving the coolant lines connected to the engine, remove the radiator from
the frame (5mm hex with 10 mm wrench).
9. Remove the master link from the chain.
10.Remove front engine mount bolt (13 mm socket, 6 mm hex key).
11.To access the swingarm bolt, remove brake lever (13 mm wrench, 5 mm hex
key).
12.Remove the swingarm bolt (22mm socket & wrench).
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NOTE:
Only drive the swingarm bolt far enough to clear the engine, leave it holding the
one side of the swingarm to the frame
13.Remove the engine from the right side of the frame.
14.Locate a suitable container for the engine coolant and remove radiator hoses
from engine (coolant will drain).
NOTE:
If the coolant looks to be free of contaminates it may be reused.
NOTE:
If you are merely performing a top end service skip ahead to Top End
Disassembly Procedure.
E2: Complete Engine Disassembly Procedure
1. Remove the magneto cover (9/64” hex key)
2. Remove the bolt from the water pump shaft (4mm) and slide off the belt cover
and the water pump belt
3. Using a flywheel holding tool and 14 mm socket remove the nut that secures
the flywheel.
4. Using the Cobra flywheel / clutch puller (#MCMUTL68), remove the flywheel
from the crankshaft.
5. Remove the stator (9/64” hex key).
6. Remove the nut holding the large gear to the transmission input shaft (19 mm
socket).
7. Remove the special nut / starter gear that holds on the clutch (special tool
available, contact your local dealer).
8. With the Cobra flywheel / clutch puller (#MCMUTL68), remove the clutch from
the crankshaft (details in Clutch Service portion of this manual).
E3: Top End Disassembly Procedure
1. Remove the cylinder head nuts (5/16”).
2. Remove the outer cylinder head.
3. Remove the inner cylinder head.
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INSPECTION NOTE:
Inspect the cylinder head for deposits and abrasions.
1. If there are deposits they should be removed
a. Black oily deposits (indicating a rich mixture or improper oil
type/quantity) can be removed with solvent
b. Crusty deposits (indicating dirt ingestion) can be removed with
solvent and may require some scraping.
2. Abrasions
a. Pitting or erosion indicates detonation and may require cylinder
head replacement, also
i. Retard the ignition timing
ii. Use a higher octane fuel
b. Missing chunks or indentations indicate broken hardware or
ingested items - replace the cylinder head.
4. Remove the cylinder.
INSPECTION NOTE:
Inspect the cylinder bore for abrasions, deposits, and missing coating.
1. If abrasions: scrapes, scratches, pitting, etc… are found, replace the
cylinder.
2. If deposits are all are found
a. Clean with muratic acid.
b. Once the deposits are removed, inspect for abrasions and missing
surface coating.
i. If there are abrasions or missing coating, replace.
ii. If all looks well, the cylinder may be saved.
Muratic acid can be dangerous. Follow the manufacturers instructions closely.
5. Remove the piston clip with a scribe.
6. Remove the piston pin with a piston pin remover.
INSPECTION NOTE:
Inspect the piston for abrasions and deposits on the top and sides and clean or
replace as necessary.
E4: Splitting the Cases
1. Remove the fasteners holding the two halves of the crankcase together.
2. Separate the cases with a proper case splitting tool.
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CAUTION:
Take caution when handling the crankshaft. It is the main power transfer to the
rest of the engine. If it is out of alignment, it will cause premature failure of your
bearings which can lead to serious damage to the cylinder and the rest of the
engine. Do not try to true the crank yourself. Truing the crank should be done
professionally.
Cobra trues every crank before it leaves the factory, and also welds the pin to
keep it true. If there are any problems send the engine in, or call tech support
(330) 549-9603 to determine what the problem is.
CAUTION:
·
If you split the cases, check the gear tooth faces for chapping & signs of
fatigue.
·
Check the small needle bearings for fatigue. If the bearings are damaged,
the engine cases should be checked to make sure the needle-bearing casing
didn’t oblong the bearing hole in the case.
·
Needle bearings should be replaced every racing season.
E5: Engine assembly
CAUTION:
For any seals that are to be installed, apply a light amount of grease to the seals’
ID and a small amount of oil to the OD.
1. Press the three bearings into the respective holes in each case half.
2. Press in the crank seals such that the concave side faces the crank weights.
3. Press in the counter shaft seal (concave side faces inside of transmission)
4. Install the water pump assembly
5. Wire ring retainer
6. Press in the water pump assembly
7. Tap both ways axially then verify easy rotation
8. Press crank into left case half
9. Insert the transmission input shaft and install large drive gear as shown in
figures 6 & 7.
NOTE:
If the nut was removed from the input shaft, it will be easier to install and tighten
later.
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Figure 6
Figure 7
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10.Insert dowel pins in the left side case as shown in figure 8.
Figure 8
11.Apply gasket sealer (NAPA Aviation Form-A-Gasket #765-1210 or equivalent)
to the mating surfaces of both crankcase halves.
12.Apply the crankcase gasket to the left crank case half being sure to install the
gasket behind the connecting rod.
13.Insert the screws with the three longer ones (40mm long) at locations shown.
Figure 9
14.Torque to 9 Nm (80 in-lb) in the pattern shown in figure 9.
15.Install the piston with new wrist pin bearing and, pin and clips.
16.Install the piston rings.
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CAUTION:
Be sure to align the piston such that the arrow on the top piston surface points to
the exhaust (front of bike/engine).
17.Apply gasket sealer (NAPA Aviation Form-A-Gasket #765-1210 or equal) to
the cylinder deck areas around the coolant passage and cylinder studs as
shown in figure 10.
Figure 10
18.Install the base gasket
19.Install the cylinder being sure that the piston rings are properly aligned with
the indexing pins.
CAUTION:
Never force the cylinder. If resistance is felt, determine the problem and solve it.
20.Install the cylinder studs and o’rings as shown in figure 11.
Figure 11
21.Install cylinder head insert.
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22.Install O’rings as shown in figure 12.
Figure 12
23.Install the cylinder head and torque to 9.2 ft-lb (12 Nm)
24.Install stator reinstalling the grommet and wires (snug the bolts).
25.Install the rotor per Rotor Installation section, under the ES4: Ignition portion
of this manual.
26.Install the water pump outlet pipe (apply Ultra black Hi-Temp RTV silicon
gasket maker to the threads before assembly) before installing the clutch and
rotate to a vertical position with the engine resting on a bench
27.Install the clutch per Clutch Installation section in this manual.
28.Install the coolant drain plug with copper washer (11 ft-lb, 15 Nm).
29.Make sure that the exhaust spacer is on the cylinder (53 in-lb, 6 Nm).
30.Install the spark plug with a fresh gasket (to apply the proper torque to the
spark plug when inserting, one must first screw the spark plug in until the
metal gasket ring causes resistance and then turn another 1/8 to ¼ turn).
31.Install reed and inlet manifold with new gaskets (58 in-lb, 6.5 Nm).
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ES3: Clutch
Cobra clutch puller assembly:
Clutch puller diagram
Figure 13
Figure 14
Tools recommended for clutch service:
·
·
22mm socket
Universal clutch puller- a universal puller that pulls the clutch, main drive gear
and rotor. (Part # MCMUTL70).
·
·
·
5mm T-handle
Clutch nut removal tool (Call local dealer for details)
Cobra 3 Shoe Clutch Milk (Part # MCMUGF01)
CLUTCH REMOVAL:
1. Drain the engine transmission oil.
2. Remove the pipe and remove the 6 bolts that hold the kick-starter cover on.
3. Remove the clutch nut (right handed nut) on the end of the crankshaft with a
22mm socket.
4. Attach the COBRA CLUTCH PULLER. There are three 6mm clutch puller
holes located on the ends of the center hub. (figures 13 & 14) You must use a
draw type puller to remove the clutch.
CAUTION:
Do not use a jaw type puller or use the 6mm tapped holes as jackscrews or you
are likely damage the clutch drum or clutch.
5. If necessary apply heat to the center clutch hub.
CAUTION:
Do not heat the crankshaft threads or the aluminum shoes.
6. Keep tension on the puller as you are heating it.
The clutch will often pop off under tension from the puller and it will be very hot.
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CLUTCH WASHER STACKUPS:
Once the clutch is removed, and cool to touch, carefully put it into a vice and
remove the center shoulder bolt out of each clutch shoe. You will probably have
to heat the center hub again to remove the bolts. Once you get a bolt loosened,
carefully remove it with the shoe and observe the way the spring washers are
stacked.
CAUTION:
It is very important that the clutch stack be reassembled as it was disassembled
unless new shoes are being installed then it is important to reinstall per figure 15.
CLUTCH ASSEMBLY REFERENCE DRAWING
REF # PART #
DESCRIPTION
1
2
3
4
CAKG0004
Set of three shoes, springs, bolts, flat washers & nuts
Set Of three springs, washers, bolts & nuts
Set of three shoes
CAMU0008
CAKG0005
HCBS5603
Single center shoulder bolt
Figure 15 Recommended clutch spring stack. Each ‘spring’ stack contains nine springs
(Bellville washers) - six arranged into three ‘flying saucers’, and three arranged in a ‘dished’
arrangement against the flat washer.
Clutch shoe wear:
·
If the clutch has been slipping and shows signs of glazing, it is best to replace
the shoes. We have found that once the shoes are glazed, even if deglazed
with emery paper or a file, the performance is reduced.
·
The best way to prevent glazing is by not gearing too high, changing the oil as
specified and by not blipping the throttle. Every time you blip the throttle, you
are working your clutch springs.
CAUTION:
The clutch produces a tremendous amount of heat and when a rider is blipping
the throttle. This makes the clutch and clutch springs wear out quicker. This also
makes your engine tend to run hotter which decreases engine power and
degrades ignition stator efficiency. It is important to train your rider NOT to be a
throttle 'blipper'.
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CAUTION:
Sludge build-up between the spring washers also keeps the clutch shoe from
engaging fully and this will cause the clutch to start to slip. So you will need to
clean the sludge out or just replace the spring washers and bolts with new ones.
How quickly this sludge builds up depends on how often you change your oil
and whether your rider is a throttle ‘blipper’.
REF #
PART NO. DESCRIPTION
ECMU0017 Crank seal
ECMU0040 Clutch to hub spacer
ECMU0003 Brass bushing
ECMU0033 Clutch Hub w/ brass bushing
CAKG0002 Clutch Complete w/ Arbor
ECMU0018 Clutch nut
1
2
3
4
5
6
Figure 16, Clutch Assembly Drawing
CLUTCH ASSEMBLY:
1. After cleaning or replacing the spring washers, reassemble the stack up of
washers.
CAUTION:
It is important to reassemble the washer stack to that recommended or to your
own specialized stack.
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CAUTION:
It is also important that all three shoes are stacked the same. (See figure 15)
2. Clean the threads of the stack bolt and the clutch with contact cleaner
removing all old thread locking material.
3. Apply high strength (red) thread lock material to the stack bolt and tighten as
tight as possible without stripping the Allen head.
CAUTION:
Avoid allowing excess thread lock material to contact the spring washers and the
clutch or the clutch is likely to malfunction.
4. Use fine emery paper on the center hole of the clutch and on the tapered
section of the crankshaft.
5. Apply a small amount of wicking / bearing retainer (green) thread lock agent
to the center tapered section of the crankshaft and taper of clutch arbor.
6. Put the clutch back in.
7. Apply high strength (red) thread locking agent to the threads and install the
nut and torque to 40 ft-lb (54Nm) with the special socket (see figure 16).
CAUTION:
Use high strength (red) thread locker on the threads of the clutch nut. If you are
using an impact socket, just zap it lightly with an air wrench to tighten it because
there are only about 4 threads inside the nut and they can be easily stripped. If
you are tightening it by hand, you can very carefully use a 3/4" piece of wooden
dowel rod inside the exhaust port to block the piston so you can tighten the nut.
Do not use something harder than your aluminum piston and do not crush the top
of the piston into the ring.
INSPECTION NOTE:
a. There must be in / out play in installed clutch (1.5 mm maximum).
b. Excess in/out will cause early crank seal failure.
c. A blue clutch drum is worn out from excessive slippage or improper
lubrication.
d. Should be no looseness in clutch shoes.
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8. Install the clutch cover taking care to put the two longer bolts in their proper
locations and tightening in the order specified in figure 17. (5mm hex key, 5.8
ft-lb, 7.8 Nm).
Figure 17
9. Put pipe back on and add oil (225 ml (7.6 oz) Cobra 3 Shoe Clutch Milk (Part
# MCMUGF01).
ES4: Ignition
Stator care:
Stator failure will result from running the bike hot. Following is a list of things that
will make your engine run hot.
1. The timing should not exceed the maximum specifications listed.
2. Improper carburetor jetting.
3. Improper spark plug heat range. Never run a hotter plug than the specified
spark plug.
4. Clutch slippage. See “CLUTCH” section for causes of slippage.
CAUTION:
·
Because of the amount of heat generated by the clutch and engine during
extended periods of riding, it is advisable to remove the ignition cover
afterward to allow the ignition to cool off. The heat transfers through the cases
and can damage the stator as it cools off because of lack of airflow around
the stator. Spray the stator and rotor with CRC 3-36 or WD-40 and let it drip
dry or blow it off a little with an air nozzle.
·
Ignition will overheat if the gap between the rotor and stator is not large
enough. There should be even clearance as the rotor rotates relative to the
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stator.
·
Non-resistor spark plug caps should be used. Resistor caps will result in a
weaker spark that will reduce performance.
·
·
Make sure ground wires are secure. If the bike is not grounded it will not run.
Make sure connections are free of dirt.
CAUTION:
If the engine is hot, it is EXTREMLY important to take the ignition cover off, put a
fan on it to let it cool, and spray it with CRC 3-36 or WD-40. If you don’t maintain
the ignition, it is destine to burn up the stator. (Stator- Part # ICMU0007)
Timing on the 2003 CM50 is very crucial. Cobra has found that the best place to
set it is at 0.050” before Top Dead Center (0.050” before the piston’s highest
point of travel). We do not recommend advancing the ignition timing as it will
cause the engine to run very hot, in-turn causing power loss, shortened clutch
life, and possibly lead to premature stator failure.
Tools recommended for timing service:
·
·
Compact motorcycle dial indicator
Universal clutch puller- a universal puller that pulls the clutch, main drive gear
and rotor. (Part # MCMUTL70).
TIMING YOUR IGNITION:
1. Remove the spark plug cap, and sparkplug.
2. Insert the dial indicator into the spark plug hole.
3. Remove the four 8/32” X 1 ¾” bolts from the ignition cover.
4. Remove the water pump belt from the rotor and water pump shaft.
5. Turn the crankshaft counterclockwise until it reaches top dead center.
6. Set the dial indicator to zero
7. Turn the crankshaft clockwise until the dial indicator reaches 0.050” (1.3 mm)
from top dead center.
8. Line up the lines on the stator and the rotor (figure 18). Otherwise loosen the
three 10X32 bolts to adjust the stator.
NOTE:
If you cannot adjust your stator, you must take the rotor off and readjust the
timing settings so the lines line up on the rotor and stator. The rotor is not keyed
to the crankshaft.
ROTOR READJUSTING:
1. Use the universal clutch puller on the rotor to remove it.
2. Insert dial indicator (figure 19).
3. Turn the crankshaft counterclockwise so it reaches top dead center.
4. Move the crankshaft clockwise to 0.050” (1.3 mm) before top dead center.
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5. Inspect and remove markings, scratches, and thread locker residue from the
rotor and crankshaft.
0.050”
before
TDC
Figure 18, Lining up the line on the rotor
with the line on the stator.
Figure 19, Using a dial indicator to measure piston
height for setting ignition timing.
ROTOR INSTALLATION:
1. Use wicking / bearing retainer (green) thread locker on the inside of the rotor,
and on tapered part of crankshaft.
CAUTION:
It is recommended that you apply the proper thread locking primer to the
components that are to receive thread locking material per the manufacturers
instructions.
2. Eyeball the lines on the rotor and stator then press the rotor onto the
crankshaft firmly (figure 18).
3. Torque the nut on the rotor to 40 ft-lb (54 Nm).
4. Recheck the timing following the procedure of timing your ignition.
5. Install the water pump belt back on.
6. Bolt the ignition cover back on.
7. Put the spark plug back in, and firmly stick the spark plug cap onto the spark
plug.
ES5: Cooling System
The water pump in the engine keeps the radiator fluid in circulation throughout
the motor. The air stream running through the radiator cools the radiator fluid.
Therefore dirty radiators additionally reduce the cooling effect.
Radiator fluid removal:
1. Remove the coolant drain plug (A) on the front of the engine case (figure 20).
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A
Figure 20
To remove radiator cap:
1. Turn the cap counter clockwise to the first stop and wait there for a few seconds.
2. Push the cap down and turn it further in the same direction and remove the cap.
NOTE: Inspect the old coolant for visual evidence of corrosion and abnormal smell.
Fill the radiator up to the bottom of the radiator filler neck with coolant. Install the cap,
turning it clockwise about ¼ turn.
Tools recommended for impeller service:
·
·
·
·
·
·
·
·
·
Flat head screwdriver
5mm hex key
13mm- hex wrench
1/8” hex key
9/64” hex key
3/32” hex key
Propane torch
3/8” diameter x 8” long steel rod
Hammer
COBRA IMPELLER SERVICE INSTRUCTIONS
1. Remove exhaust pipe and gas tank (you will be using a propane torch in step 12.
2. Remove radiator cap and drain engine coolant by removing the 13mm- hex head
coolant drain plug.
3. If the impeller is damaged or broken completely back flush the coolant system to
ensure no solid pieces are in the system.
4. Remove foot brake.
5. Drain engine transmission oil by removing drain screw using a 13mm- hex
wrench. (item 2 in the figure below).
6. Remove kick-starter cover using a 5mm hex key. (item 3 six places)
7. Remove clutch and basket.
8. Unscrew water elbow fitting. (Figure 21)
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Figure 21
8. Remove ignition cover using a 9/64” hex key (four places)
9. Remove belt retainer screw using a 1/8” hex key. (Figure 22 - item 1)
10.Remove belt retainer, water pump belt and water pump fan pulley.
11.Remove bearing retainer screw using a 3/32” hex key. (Figure 22 – item 2)
Figure 22
12.Heat engine case around area of impeller lightly with a small Burnsmatic propane
torch. Using a 3/8” diameter x 8” long steel rod, tap impeller assembly out of
engine as shown in figure 23.
Figure 23
CAUTION:
Too much heat can be detrimental to the engine cases.
13.The shaft assembly is serviceable. Use a 1/8” hex key to remove impeller
retainer screw. Remove impeller, seal and both bearings. Check shaft for wear in
the area of the seal. If there is any sign of wear (like a groove) replace the shaft.
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Figure 24
14.Reinstall new bearings, seal and impeller. Clean all threads and use green
(wicking / bearing retainer) thread locker.
15.Using a liberal amount of grease on the outside seal, bearings and inside of
case, reinstall bearing assembly by using a 0.500” ID by 1.000” OD steel tube 2”
long and tap on end of tube per figure 25.
Figure 25
16.Re-assemble in same order of disassembly. Clean all threads and use green
(wicking / bearing retainer) thread locker on the belt retainer screw.
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ES6: Fuel & Air System
Carburetor:
Tools recommended for carburetor service:
·
·
·
Small flat head screwdriver
WD-40
8mm socket
KING Carburetor Ref. Drawing
REF. #
1
2
3
4
PART #
RCMU0305
RCMU0601
RCMU0002
DESCRIPTION
CARB SLIDE
NEEDLE
ATOMIZER
MAIN JET
5
PILOT JET
6
7
8
CHOKE JET
FLOAT
RUBBER CABLE CAP SEAL
CABLE ADJUSTER
RCMU0301
RCMU0102
RCMU0003
9
10
11
12
RCMU0006
RCMU0106
TOP CARB SCREW
CARB TOP
13
14
15
16
17
20
21
25
ZCMU0007
RCMU0004
RCMU0205
RCMU0007
RCMU0204
RCMU0009
RCMU0011
RCMU0103
TOP CARB GASKET
SLIDE SPRING
NEEDLE RETAINER PLATE
NEEDLE CLIP
CHOKE ASS’Y. 2001 CM
FUEL MIXTURE SCREW
IDLE ADJUSTMENT SCREW
FLOAT BOWL GASKET
26
27
28
29
30
31
RCMU0107
RCMU0012
RCMU0016
RCMU0106
FLOAT NEEDLE
DIFFUSER
FLOAT RETAINER PIN
FLOAT BOWL
RCMU0201
BOTTOM FLOAT SCREW
33
RCMU0269
VELOCITY STACK
Figure 26
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Your Cobra is equipped with an adjustable carburetor. Some fine-tuning may be
needed according to weather condition and altitude. Proper jetting is very
important for engine performance and engine life. Serious damage to the engine
can occur if not properly adjusted.
IDLE ADJUSTMENT:
On the left side of the carburetor, there are two adjustment screws. The larger
screw with the knurled head is the idle adjustment screw. To raise the idle, turn
the screw in clockwise (in 1/4 turn increments) and rev the engine after each
adjustment. To lower the idle, turn the screw counter-clockwise.
TOP END JETTING:
Indications that the engine is running too rich (too much fuel for the air) are:
·
·
·
Engine not revving out or blubbering at high RPMs.
Engine will not ‘clean out’
Wet or black spark plug
NOTE: Before changing jetting be sure that the air filter is properly cleaned and
has the usual amount of air filter oil. An overly dirty air filter can cause the engine
to run rich.
If the engine is running rich on the top end it should be leaned out. Leaning it out
can be done by:
1. Changing the main jet to a smaller number.
2. Raising the needle clip (this lowers the jet needle) one notch at a time on the
slide.
Indications that the engine is running too lean are:
·
·
·
Engine cutting out on top end.
Engine overheating and ultimately seizure.
White spark plug
CAUTION:
It is much safer to operate the engine slightly rich as opposed to slightly lean.
This is because an overly rich engine will just run poorly while an overly lean
engine will seize, potentially causing an expensive top end rebuild and a DNF.
To richen the carburetor:
1. Change the main jet one number at a time (larger).
2. Lower the needle clip (raising the jet needle) one notch at a time until the
engine starts to blubber on the top end, then move the clip back up one notch
or until you get the blubber out.
FUEL MIXTURE SCREW
The smaller brass screw that is towards the front of the engine is a fuel mixture
screw. This screw will also richen and lean your engine more on the bottom and
mid-range. In warmer conditions, turn the screw in. In colder conditions, turn the
screw out. Be sure to keep the carburetor very clean and make sure you don't
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have water or dirt in the carburetor bowl. Use automotive carburetor cleaner or
WD-40 to clean the carburetor inside and out.
STOCK CARBURETOR SETTINGS
The 2003 KING stock carburetor settings from the factory are:
·
·
65 pilot jet
94 main jet
Cleaning the carburetor:
Clean the carburetor in a well-ventilated area, and take care that there is no
spark or flame anywhere near the working area; this includes any appliance with
a pilot light. Because of the danger of highly flammable liquids, do not use
gasoline or low flash-point solvent to clean the carburetor.
1. Make sure the fuel is shut off.
2. Remove the carburetor.
3. Drain the fuel in the carburetor.
4. Disassemble the carburetor.
CAUTION:
Do not use compressed air on an assembled carburetor. Or the pressure may
deform the float. Do not use a strong carburetor cleaning solution, which could
attack the parts of the carburetor; instead, use a mild high cleaning solution safe
for plastic parts.
5. Immerse all the metal parts in a carburetor cleaning solution.
6. Rinse the parts in water.
7. After the parts are cleaned, dry them with compressed air.
8. Blow out the fuel passages with compressed air.
9. Assemble the carburetor
10. Install the carburetor onto the motorcycle.
NOTE:
The three most common problems with
this carburetor are (figure 27):
1. Installing the carburetor top
backwards, and
2. The carburetor slide indexing pin
falling out.
3. Either side vent elbow falling out.
Figure 27 Proper carburetor top
installation
and
location
of
rectangular slide indexing pin and
one of the elbows that has been
known to fall out.
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Reeds:
·
·
·
·
The reeds must lay flat on the reed cage.
If the reed tips aren’t lying flat, replace them immediately.
The reeds must have a tight seal on the reed cage.
If the reed is damaged in any way, replace it. This means cracks, chips,
and ruptures. Anything abnormal, replace the reeds.
Take the reed cage out and hold it up to the light and look in through the cage. If
you see light between the reed pedals and the frame, then replace the reeds. If
you do not see light, then the reeds should be ok. (See figure 28)
Figure 28
The presence of light indicates that the reeds should be replaced, or possibly turned over.
ES7: Exhaust
The pipe is a crucial element to a motorcycle. Any kinks, dents, or damage done
to the pipe will result in a major performance loss.
NOTE:
Be sure to take the pipe off, and any carbon that may be built up. Carbon build
up is created from exhaust. Exhaust has oils in it, and the oils cling to the walls
of the inside of the pipe. Over a long period of time, the diameter of the pipe will
decrease, due to carbon build up. So it is essential to clear the residue.
CAUTION:
It is important to repack the silencer. Signs of your silencer needing to be
repacked are:
·
·
The bike is louder than normal.
A loss of power.
39
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Chassis Service / Parts
CS1: Wheels & Tires
Rear wheel
Rear wheel dampening
Tools recommended for wheel service:
·
·
·
·
13mm socket
Flathead screwdriver
11mm wrench or socket
19mm wrench
The Cobra is the only 50cc to have the rear wheel damping system. This feature
prevents engine impact shock caused by hard landings. This design allows the
cushioned sprocket to move forward and backwards separately from the wheel.
After each moto, check the 4 rubber dampers, spacers and bolts for fatigue. You
should keep extra rubber dampers in your toolbox (part # PCMU0059). Different
sized sprockets are also available.
Watch for bending and warping of the outside rear damper plate. If it is bent or
warped, the rubber dampers in the sprockets do not last as long as when using a
straight unit. Usually you can straighten the plate with a hammer or just flip it
over.
Changing the rubber dampers:
1. Remove the four bolts with the 11mm wrench
2. Take the backing plate off
3. Observe the four rubber dampers, and pull the sprocket upward to remove it.
1. Pop the four rubber dampers out of
the sprocket.
2. Push the rubber dampers into the
sprocket.
3. Place the sprocket with rubber
dampers, onto the aluminum studs.
4. Place backing plate over the dampers
and sprocket.
5. Insert the 11mm bolts into the holes
and tighten to 18 ft-lb (24 Nm).
Figure 29
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Rear wheel pullers
Disassembly:
1. Remove axle, and
back wheel assembly.
2. Pull the rear wheel
pullers out of the back
of the swing arm.
Figure 30
Rear wheel alignment:
1. Measure from the side of
the swing arm to the outer
edge of the rim and make
sure both sides are equal.
2. Adjust the wheel pull bolt
on the rear wheel puller to
get the distance from the
swing arm to the rim
about the same.
Figure 31
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Front wheel assembly
2003 FRONT WHEEL ASSEMBLY
REF. #
PART #
HCNS1201
KCKG0029
WCMU0023
WAKG0005
WCMU0001
BCKG0008
KCKG0028
WCMU0016
DESCRIPTION
12mm AXLE NUT
1
2
3
4
5
6
7
8
FORK LEG (NONBRAKE SIDE)
WHEEL SPACER (LARGE)
FRONT WHEEL (COMPLETE)
WHEEL SPACER (SMALL)
FRONT BRAKE MOUNT
FORK LEG (BRAKE SIDE)
REAR AXLE
Figure 32
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CS2: Brakes
Front Brakes
The front brake is fully hydraulic.
WARNING! Your front brake needs a break-in period to achieve maximum brake
power. 30-40 stops will bring the brake to peak performance.
Check before each ride:
·
Make sure the brake does not have any leaks by holding the lever in while
checking hose connections.
·
Make sure the brake lever pressure is OK by pulling in on the lever and
ensuring full braking performance is achieved before the lever touches the
handlebar. If this is not the case, pump the lever several times until the lever
feels firm.
·
·
Always make sure the rotor and brake pads are free from oil and grease.
Clean the rotor with mild dish soap or alcohol. Contaminated pads must be
replaced.
Do not remove the brake lever unless you want to bleed the brake!!! The
piston will come out along with the oil behind it unless you keep it held in the
master cylinder.
CAUTION:
This brake uses low viscosity mineral oil available from a Cobra Dealer. DO
NOT EVER USE DOT BRAKE FLUID!!!
Brake Pad removal procedure:
1) Remove brake caliper using 4mm Allen wrench as shown
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Figure 33
2) Remove cotter key from caliper as shown and pull pads out.
Figure 34
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3) Brake pads must be checked periodically for wear. They are also available
from a Cobra dealer. The brake pad must be a minimum thickness of 2.5mm.
This is measuring the pad + the holder as shown below.
Figure 35
Brake bleeding procedure:
1) Remove brake caliper using 4mm Allen wrench as shown in pad removal
procedure. Pry pads outward to fully retracted position.
2) Remove reservoir cap using a Torx T25 wrench as shown. Keep reservoir
level.
Figure 36
3. Remove bleed screw on caliper using a 3mm Allen wrench as shown.
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Figure 37
4) Attach Bleeding syringe as shown. Pump all air out of system until only clean
oil runs out of reservoir.
Figure 38
5) Reinstall reservoir cap. Oil will overflow in the process. This is necessary to
ensure no air is in the system.
Remove bleeding syringe and quickly reinstall bleed screw.
46
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CS2: Suspension
Rear Shock
Figure 39
DESCRIPTION
COBRA PART NUMBER
SCKGOH01
SCKGOH02
SCKGOH03
SCKGOH04
SCKGOH05
SCKGOH06
SCKGOH07
SCKG0H08
SCKGOH09
SCKGOH10
SCKGOH11
SCKGOH12
SCKGOH13
SCKGOH14
SCKGOH15
SCKGOH16
SCKGOH17
SCKGOH18
SCKGOH19
SCKGOH20
SCKGOH21
SCKGOH22
SPRING CLIP
SPACER
BALL JOINT
SPRING PLATFORM
LOCKNUT
SLEEVE
BUMPER RUBBER
SPRING - LIGHT
SPRING-MEDIUM-STOCK
SPRING-HEAVY
ORING FOR BALL JOINT
ORING FOR REBOUND ADJUSTER
ORING FOR REBOUND ADJUSTER
SUPPORT SLEEVE
CIRCLIP
PIN FOR REBOUND ADJUST
ADJUSTMENT KNOB
SHAFT FOR END EYE
NUT
END EYE
SCREW FOR KNOB
KNOB FOR ADJUSTMENT
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Front forks
Tools recommended for front fork service:
·
·
·
·
·
·
·
Flat head screwdriver
Hammer
Snap ring pliers
Seal drivers
13mm wrench
1 1/8” wrench or socket
5 wt fork oil
FORK ASSEMBLY PROCEDURES:
Figure 40
1. Slide swiper (#6) onto lower fork leg.
2. Slide snap ring (#5) onto lower fork leg.
3. CAREFULLY slide seal (#4) onto lower fork leg with spring facing away from
snap ring.
4. Slide bronze bushing (#3) onto lower fork leg.
5. Install Teflon bushing into groove on lower fork leg.
Figure 41
6. Slide the bronze bushing over the Teflon bushing about 1/4" to hold the
Teflon in the groove.
7. Insert the lower leg assembly into the upper fork tube about 5-6".
8. Use a seal driver to drive the seal into the upper tube.
9. Install the snap ring. Make sure it is properly seated in the groove.
10.Snap the swiper into the groove in the upper tube.
11.Fill with 4.0 oz (118 ml) 5 wt fork oil (should measure 130 mm (5.1”) from top
of tube with spring removed.
12.Install the fork spring
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13.Connect the cartridge rod to the cap and tighten to 12 ft-lb (9 Nm).
CAUTION:
The damper rod is hollow and will break if the nut is over tightened (proper torque
is 12 ft-lb, 16 Nm).
KING FORK Ref. KING FORK Ref.
Drawing
Drawing
DESCRIPTION
REF. REF.
#
PART #
#
FORK ASSY. BRAKE
SIDE
FORK ASSY.
NON BRAKE SIDE
1
1
KAKG0005
KAKG0006
2
3
2
3
KAKG0030 FORK CAP
KCKG0021 FORK LEG - OUTER
FORK LEG-INNER
BRAKE SIDE
4
4
KAKG0028
FORK LEG-INNER
NON BRAKE SIDE
KAKG0029
5
6
5
6
KCKG0027 DAMPER ROD
KCKG0007 FORK SPRING 7#
FORK SPRING 9#
(STOCK)
KCKG0009
KCKG1200 FORK SPRING 12#
KCKG0023 CARTRIDGE TUBE
HCNL5601 LOCK NUT-FORK CAP
KCKG0032 FORK SPRING GUIDE
ZCMUOR08 O-RING FORK CAP
KCKG0033 FORK BUSHING-OUTER
KCKG0025 CARTRIDGE TOP
7
8
9
10
11
12
7
8
9
10
11
12
14
15
16
17
18
19
20
14
15
16
17
18
19
20
KCMU0008 SWIPER
KCMUSR23 SNAP RING
KCMU0007 FORK SEAL
KCKG0020 FORK BUSHING-INNER
HCBC0625 BOLT-DAMPER ROD
KCKG0035 BUSHING-PISTON
KCKG0026 FORK PISTON
BASE VALVE ASSY.
(SOFT)
21A 21A
21B 21B
21A 21C
KAKG0013
BASE VALVE ASSY.
KAKG0014
MEDIUM (STOCK)
BASE VALVE ASSY.
(HARD)
KAKG0015
O-RING - BASE VALVE
ZCKGOR10
22
22
ASSEMBLY
23
24
23
24
KCKG0031 TOP OUT SPRING
KCKG0024 FORK BOTTOM PLUG
Figure 42
Because of different rider weights, sizes and riding styles, we offer various
suspension options:
See Optional Components section of this manual for details on these and other
optional components for your Cobra Motorcycle.
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Troubleshooting
1) Engine not behaving properly
a) Carburetor top is installed backwards (happens a lot)
b) The carburetor slide indexing pin is missing
2) Engine is down on power
a) Clutch engagement is not set properly
b) Jetting is incorrect
c) Silencer needs repacked
d) Exhaust pipe
i) Has excess carbon buildup
ii) Has large dent in it
e) Compression is low
i) Piston
ii) Rings
f) Reeds are damaged
g) Ignition timing is incorrect
3) Engine is excessively loud
a) Silencer needs repacking
4) Engine ‘blubbers’ at high RPMs
a) Jetting too rich
5) Engine won’t start
a) Fuel
i) None in tank
ii) Is sour or bad
b) Carburetor is dirty
c) Ignition
i) Spark plug fouled
ii) Spark plug cap off
iii) Engine Shut-off ‘kill’ switch is shorted
iv) Bad electrical ground
v) Stator winding damaged
d) Exhaust is plugged
6) Engine won’t idle
a) Idle knob needs adjusted
b) Carburetor jets are dirty
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Index
Air Filter..............................................13
Brakes
Recommended ...............................4
Maintenance
Front ...............................................43
Break-In................................................7
Carburetion
Schedule ..........................................9
Tips...................................................9
Oil
Specifications..................................4
Carburetor .........................................36
Chain
Recommended ...............................4
Optional components.........................5
Parts List
Adjustment.....................................12
Chassis
Carburetor .....................................36
Clutch 1 ..........................................27
Clutch 2 ..........................................28
Engine ............................................15
Pullers ................................................41
Rear
Specification....................................4
Clutch
Parts List 1.....................................27
Parts List 2.....................................28
Service ...........................................26
Clutch Lubricant
Shock..............................................47
Rear Brake
Replacing .......................................10
Compression test .............................18
Cooling System.................................32
Cylinder head
torque ...............................................6
Damper ..............................................40
Engine
Parts List........................................15
Specifications..................................4
Exhaust..............................................39
Flywheel
Torque ..............................................6
Fork oil replacement ........................13
Forks...................................................48
Front
Brakes............................................43
Forks...............................................48
Front Wheel.......................................42
Fuel System
Parts list .........................................36
Service ...........................................36
General Tips........................................9
Ignition
Service ...........................................30
Timing.............................................31
Jetting
How To ...........................................37
Stock.................................................4
Lubrication
Adjustment.....................................12
Rear Wheel
Damper ..........................................40
Pullers ............................................41
Reeds.................................................39
Rotor
torque ...............................................6
Shock..................................................47
Spark Plug
Recommended ...............................4
Specifications......................................4
Torque Values.................................6
Starting .................................................8
Stator
torque ...............................................6
Suspension........................................47
Tips.......................................................9
Top End
Service ...........................................17
Transmission
Specifications..................................4
Transmission Lubricant
Replacing .......................................10
Troubleshooting ................................50
VIN reading .........................................9
WARNING ...........................................2
Wheels
Service ...........................................40
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