Honda Automobiles GX390 User Manual

Owner’s Manual  
GX270GX390  
LPG-Fueled Engine  
2003 Honda Motor Co., Ltd. -All Rights Reserved  
The engine exhaust from this product  
contains chemicals known to the State  
of California to cause cancer, birth  
defects or other reproductive harm.  
Keep this owner’s manual handy, so you can refer to it at any time.  
This owner’s manual is considered a permanent part of the engine and  
should remain with the engine if resold.  
The information and specifications included in this publication were in  
effect at the time of approval for printing. Illustrations are based on the  
GX270 LPG. Honda Motor Co., Ltd. reserves the right, however, to  
discontinue or change specifications or design at any time without  
notice and without incurring any obligation whatever. No part of this  
publication may be reproduced without written permission.  
INTRODUCTION  
Congratulations on your selection of a Honda engine. We are certain  
you will be pleased with your purchase of one of the finest engines on  
the market.  
We want to help you get the best results from your new engine and to  
operate it safely. This manual contains the information on how to do  
that; please read it carefully.  
As you read this manual, you will find information preceded by a  
symbol. That information is intended to help you avoid  
damage to your engine, other property, or the environment.  
We suggest you read the warranty policy to fully understand its  
coverage and your responsibilities of ownership. The warranty policy  
is a separate document that should have been given to you by your  
dealer.  
When your engine needs scheduled maintenance, keep in mind that  
your Honda servicing dealer is specially trained in servicing Honda  
engines. Your Honda servicing dealer is dedicated to your satisfaction  
and will be pleased to answer your questions and concerns.  
Best Wishes,  
Honda Motor Co., Ltd.  
1
INTRODUCTION  
A FEW WORDS ABOUT SAFETY  
Your safety and the safety of others are very important. And using this  
engine safely is an important responsibility.  
To help you make informed decisions about safety, we have provided  
operating procedures and other information on labels and in this  
manual. This information alerts you to potential hazards that could  
hurt you or others.  
Of course, it is not practical or possible to warn you about all the  
hazards associated with operating or maintaining an engine. You must  
use your own good judgment.  
You will find important safety information in a variety of forms,  
including:  
Safety Labels on the engine.  
Safety Messages preceded by a safety alert symbol  
of three signal words, DANGER, WARNING, or CAUTION.  
and one  
These signal words mean:  
You WILL be KILLED or SERIOUSLY HURT if  
you don’t follow instructions.  
You CAN be KILLED or SERIOUSLY HURT if  
you don’t follow instructions.  
You CAN be HURT if you don’t follow  
instructions.  
Safety Headings such as IMPORTANT SAFETY INFORMATION.  
Safety Section such as ENGINE SAFETY.  
Instructions how to use this engine correctly and safely.  
This entire book is filled with important safety information  please  
read it carefully.  
2
CONTENTS  
ENGINE SAFETY ........................................................................................ 5  
IMPORTANT SAFETY INFORMATION ................................................. 5  
CONTROLS & FEATURES ......................................................................... 7  
COMPONENT & CONTROL LOCATIONS ............................................. 7  
CONTROLS ............................................................................................. 8  
Engine Switch ..................................................................................... 8  
Choke Lever ........................................................................................ 9  
Throttle Lever ................................................................................... 10  
Recoil Starter Grip ............................................................................ 10  
FEATURES ............................................................................................ 11  
Oil Alert System (applicable engine types) .................................. 11  
BEFORE OPERATION .............................................................................. 12  
IS YOUR ENGINE READY TO GO? ...................................................... 12  
Check the General Condition of the Engine ................................... 12  
Check the Engine .............................................................................. 13  
Check the Equipment Powered by This Engine ............................. 13  
OPERATION ............................................................................................. 14  
SAFE OPERATING PRECAUTIONS .................................................... 14  
STARTING THE ENGINE ..................................................................... 14  
STOPPING THE ENGINE ..................................................................... 18  
SETTING ENGINE SPEED .................................................................... 19  
SERVICING YOUR HONDA ENGINE ...................................................... 20  
THE IMPORTANCE OF MAINTENANCE ............................................. 20  
MAINTENANCE SAFETY ..................................................................... 21  
MAINTENANCE SCHEDULE ............................................................... 22  
FUEL RECOMMENDATIONS .............................................................. 23  
ENGINE OIL LEVEL CHECK ................................................................. 24  
ENGINE OIL CHANGE .......................................................................... 25  
ENGINE OIL RECOMMENDATIONS ................................................... 26  
AIR FILTER INSPECTION ..................................................................... 27  
AIR CLEANER SERVICE ....................................................................... 28  
SPARK PLUG SERVICE ........................................................................ 30  
IDLE SPEED ADJUSTMENT ................................................................ 31  
SPARK ARRESTER SERVICE (optional part) ...................................... 32  
3
CONTENTS  
HELPFUL TIPS & SUGGESTIONS .......................................................... 33  
STORING YOUR ENGINE .................................................................... 33  
Storage Preparation ......................................................................... 33  
Storage Precautions ......................................................................... 34  
Removal From Storage .................................................................... 35  
TRANSPORTING .................................................................................. 36  
TAKING CARE OF UNEXPECTED PROBLEMS ...................................... 37  
ENGINE WILL NOT START .................................................................. 37  
ENGINE LACKS POWER ...................................................................... 37  
TECHNICAL & CONSUMER INFORMATION ......................................... 38  
TECHNICAL INFORMATION ................................................................ 38  
Serial Number Location ................................................................... 38  
Remote Control Linkage .................................................................. 39  
Carburetor Modification for High Altitude Operation.................... 40  
Emission Control System Information ........................................... 41  
Air Index ............................................................................................ 43  
Specifications ................................................................................... 44  
Wiring Diagram ................................................................................ 45  
CONSUMER INFORMATION ............................................................... 46  
Honda Publications .......................................................................... 46  
Warranty Service Information ......................................................... 47  
QUICK REFERENCE INFORMATION ............................. Inside back cover  
4
ENGINE SAFETY  
IMPORTANT SAFETY INFORMATION  
Most accidents with engines can be prevented if you follow all  
instructions in this manual and on the engine. Some of the most  
common hazards are discussed below, along with the best way to  
protect yourself and others.  
Owner Responsibilities  
Honda engines are designed to give safe and dependable service if  
operated according to instructions. Read and understand this  
owner’s manual before operating the engine. Failure to do so could  
result in personal injury or equipment damage.  
Know how to stop the engine quickly, and understand the operation  
of all controls. Never permit anyone to operate the engine without  
proper instructions.  
Do not allow children to operate the engine. Keep children and pets  
away from the area of operation.  
Refuel With Care  
LPG is extremely flammable, and LPG can explode. Refuel outdoors, in  
a well-ventilated area, with the engine stopped. Never smoke near LPG,  
and keep other flames and sparks away.  
Hot Exhaust  
The muffler becomes very hot during operation and remains hot for  
a while after stopping the engine. Be careful not to touch the muffler  
while it is hot. Let the engine cool before storing it indoors.  
To prevent fire hazards and to provide adequate ventilation for  
stationary equipment applications, keep the engine at least 3 feet (1  
meter) away from building walls and other equipment during  
operation. Do not place flammable objects close to the engine.  
5
ENGINE SAFETY  
Carbon Monoxide Hazard  
Exhaust gas contains poisonous carbon monoxide. Avoid inhalation of  
exhaust gas. Never run the engine in a closed garage or confined area.  
Other Equipment  
Review the instructions provided with the equipment powered by this  
engine for any additional safety precautions that should be observed  
in conjunction with engine startup, shutdown, or operation, or  
protective apparel that may be needed to operate the equipment.  
6
CONTROLS & FEATURES  
COMPONENT & CONTROL LOCATIONS  
MUFFLER  
AIR CLEANER  
THROTTLE LEVER  
SPARK PLUG  
CHOKE LEVER  
STARTER GRIP  
RECOIL STARTER  
ENGINE SWITCH  
OIL DRAIN PLUG  
OIL FILLER CAP  
7
CONTROLS & FEATURES  
CONTROLS  
Engine Switch  
The engine switch enables and disables the ignition system.  
The engine switch must be in the ON position for the engine to run.  
Turning the engine switch to the OFF position stops the engine.  
ENGINE SWITCH  
OFF  
ON  
8
CONTROLS & FEATURES  
Choke Lever  
The choke lever opens and closes the choke valve in the carburetor.  
The CLOSED position creates a vacuum to help the LPG to flow into  
the engine during starting.  
The OPEN position removes the vacuum after the engine has started  
and can produced its own vacuum.  
Some engine applications use a remotely-mounted choke control  
rather than the engine-mounted choke lever shown here.  
CHOKE LEVER  
CLOSED  
OPEN  
9
CONTROLS & FEATURES  
Throttle Lever  
The throttle lever controls engine speed.  
Moving the throttle lever in the directions shown makes the engine  
run faster or slower.  
Some engine applications use a remotely-mounted throttle control  
rather than the engine-mounted throttle lever shown here.  
THROTTLE LEVER  
FAST  
SLOW  
Recoil Starter Grip  
Pulling the starter grip operates the recoil starter to crank the engine.  
STARTER GRIP  
10  
CONTROLS & FEATURES  
FEATURES  
Oil Alert System (applicable engine types)  
The Oil Alert system is designed to prevent engine damage caused  
by an insufficient amount of oil in the crankcase. Before the oil level in  
the crankcase can fall below a safe limit, the Oil Alert system will  
automatically stop the engine (the ignition switch will remain in the  
ON position).  
If the engine stops and will not restart, check the engine oil level (page  
24) before troubleshooting in other areas.  
11  
BEFORE OPERATION  
IS YOUR ENGINE READY TO GO?  
For your safety, and to maximize the service life of your equipment, it  
is very important to take a few moments before you operate the  
engine to check its condition. Be sure to take care of any problem you  
find, or have your servicing dealer correct it, before you operate the  
engine.  
Improperly maintaining this engine,  
or failing to correct a problem  
before operation, could cause a  
malfunction in which you could be  
seriously injured.  
Always perform a preoperation  
inspection before each operation,  
and correct any problem.  
Before beginning your preoperation checks, be sure the engine is level  
and the engine switch is in the OFF position.  
Check the General Condition of the Engine  
Look and smell around and underneath the engine for signs of oil or  
LPG leaks.  
Remove any excessive dirt or debris, especially around the muffler  
and recoil starter.  
Look for signs of damage.  
Check that all shields and covers are in place, and all nuts, bolts, and  
screws are tightened.  
12  
BEFORE OPERATION  
Check the Engine  
Check the engine oil level (see page 24). Running the engine with a  
low oil level can cause engine damage.  
The Oil Alert system (applicable engine types) will automatically  
stop the engine before the oil level falls below safe limits. However,  
to avoid the inconvenience of an unexpected shutdown, always  
check the engine oil level before startup.  
Check the air filter (see page 27 ). A dirty air filter will restrict air flow  
to the carburetor, reducing engine performance.  
Check the Equipment Powered by This Engine  
Review the instructions provided with the equipment powered by this  
engine for any precautions and procedures that should be followed  
before engine startup.  
13  
OPERATION  
SAFE OPERATING PRECAUTIONS  
Before operating the engine for the first time, please review the  
IMPORTANT SAFETY INFORMATION on page 5 and the chapter titled  
BEFORE OPERATION.  
Carbon monoxide gas is toxic.  
Breathing it can cause  
unconsciousness and even kill you.  
Avoid any areas or actions that  
expose you to carbon monoxide.  
Review the instructions provided with the equipment powered by this  
engine for any safety precautions that should be observed in  
conjunction with engine startup, shutdown, or operation.  
STARTING THE ENGINE  
1.Turn the fuel valve to the OPEN or ON position at the source before  
attempting to start the engine.  
14  
OPERATION  
2. Move the choke lever to the CLOSED position.  
Always use the choke when starting the engine.  
Some engine applications use a remotely-mounted choke control  
rather than the engine-mounted choke lever shown here.  
CHOKE LEVER  
CLOSED  
3. Move the throttle lever away from the SLOW position, about 1/3 of  
the way toward the FAST position.  
Some engine applications use a remotely-mounted throttle control  
rather than the engine-mounted throttle lever shown here.  
THROTTLE LEVER  
SLOW  
15  
OPERATION  
4. Turn the engine switch to the ON position.  
ENGINE SWITCH  
ON  
5. Operate the starter.  
Pull the starter grip lightly until you feel resistance, then pull briskly.  
Return the starter grip gently.  
STARTER GRIP  
16  
OPERATION  
6. Move the choke lever to the OPEN position after the engine has  
started.  
CHOKE LEVER  
OPEN  
17  
OPERATION  
STOPPING THE ENGINE  
To stop the engine in an emergency, simply turn the engine switch to  
the OFF position. Under normal conditions, use the following  
procedure.  
1. Move the throttle lever to the SLOW position.  
Some engine applications use a remotely-mounted throttle control  
rather than the engine-mounted throttle lever shown here.  
THROTTLE LEVER  
SLOW  
2. Turn the engine switch to the OFF position.  
ENGINE SWITCH  
OFF  
3. Turn the fuel valve to the CLOSED or OFF position at the source.  
18  
OPERATION  
SETTING ENGINE SPEED  
Position the throttle lever for the desired engine speed.  
Some engine applications use a remotely-mounted throttle control  
rather than the engine-mounted throttle lever shown here.  
For engine speed recommendations, refer to the instructions provided  
with the equipment powered by this engine.  
THROTTLE LEVER  
FAST  
SLOW  
19  
SERVICING YOUR ENGINE  
THE IMPORTANCE OF MAINTENANCE  
Good maintenance is essential for safe, economical, and trouble-free  
operation. It will also help reduce air pollution.  
Improperly maintaining this engine,  
or failure to correct a problem  
before operation, can cause a  
malfunction in which you can be  
seriously hurt or killed.  
Always follow the inspection and  
maintenance recommendations and  
schedules in this owner’s manual.  
To help you properly care for your engine, the following pages include  
a maintenance schedule, routine inspection procedures, and simple  
maintenance procedures using basic hand tools. Other service tasks  
that are more difficult, or require special tools, are best handled by  
professionals and are normally performed by a Honda technician or  
other qualified mechanic.  
The maintenance schedule applies to normal operating conditions. If  
you operate your engine under unusual conditions, such as sustained  
high-load or high-temperature operation, or use in unusually wet or  
dusty conditions, consult your servicing dealer for recommendations  
applicable to your individual needs and use.  
Maintenance, replacement or repair of emission control devices and  
systems may be done by any engine repair establishment or  
individual, using parts that are ‘‘certified’’ to EPA standards.  
20  
SERVICING YOUR ENGINE  
MAINTENANCE SAFETY  
Some of the most important safety precautions follow. However, we  
cannot warn you of every conceivable hazard that can arise in  
performing maintenance. Only you can decide whether or not you  
should perform a given task.  
Failure to properly follow  
maintenance instructions and  
precautions can cause you to be  
seriously hurt or killed.  
Always follow the procedures and  
precautions in the owner’s manual.  
Safety Precautions  
Make sure the engine is off before you begin any maintenance or  
repairs. This will eliminate several potential hazards:  
Carbon monoxide poisoning from engine exhaust.  
Be sure there is adequate ventilation whenever you operate the  
engine.  
Burns from hot parts.  
Let the engine and exhaust system cool before touching.  
Injury from moving parts.  
Do not run the engine unless instructed to do so.  
Read the instructions before you begin, and make sure you have the  
tools and skills required.  
To reduce the possibility of fire or explosion, be careful when  
working around LPG. Keep cigarettes, sparks and flames away from  
all fuel-related parts.  
Remember that your servicing dealer knows your engine best and is  
fully equipped to maintain and repair it.  
To ensure the best quality and reliability, use only new, genuine  
Honda parts or their equivalents for repair and replacement.  
21  
SERVICING YOUR ENGINE  
MAINTENANCE SCHEDULE  
REGULAR SERVICE PERIOD (3)  
ITEM  
Each  
use  
First  
month 3 months6 months year  
or or or or  
20 Hrs. 50 Hrs. 100 Hrs. 200 Hrs.  
Every  
Every  
Every  
Refer  
to  
Perform at every indicated  
month or operating hour interval,  
whichever comes first.  
page  
Engine oil  
Check level  
24  
25  
(LPG model)  
Reduction gear oil  
(Equipped model)  
Air filter  
Change  
Check level  
Change  
Check  
27  
Clean  
(1)  
28  
Replace  
Clean  
()  
Sediment cup  
Spark plug  
Check-adjust  
Replace  
Clean  
30  
Spark arrester  
(optional parts)  
Idle speed  
32  
Check-adjust  
Check-adjust  
Clean  
(2)  
(2)  
31  
Valve clearance  
Combustion chamber  
After every 250 Hrs (2)  
Fuel tube (LPG model) Check  
Fuel tube Check  
Every 2 years (Replace if necessary) (2)  
Emission-related items.  
() Replace the paper element type only.  
(1) Service more frequently when used in dusty areas.  
(2) These items should be serviced by your servicing dealer, unless  
you have the proper tools and are mechanically proficient. Refer  
to Honda shop manual for service procedures.  
(3) For commercial use, log hours of operation to determine proper  
maintenance intervals.  
22  
SERVICING YOUR ENGINE  
FUEL RECOMMENDATIONS  
Use LPG with a propane content of 95% or higher.  
This engine is certified to operate on LPG only.  
Occasionally you may hear a light ‘‘spark knock’’ or ‘‘pinging’’  
(metallic rapping noise) while operating under heavy loads. This is no  
cause for concern.  
If spark knock or pinging occurs at a steady engine speed, under  
normal load, change brands of LPG. If spark knock or pinging persists,  
see an authorized Honda servicing dealer.  
Running the engine with persistent spark knock or pinging can cause  
engine damage.  
Running the engine with persistent spark knock or pinging is misuse,  
and the Distributor’s Limited Warranty does not cover parts damaged  
by misuse.  
23  
SERVICING YOUR ENGINE  
ENGINE OIL LEVEL CHECK  
Check the engine oil level with the engine stopped and in a level  
position.  
1. Remove the filler cap/dipstick and wipe it clean.  
2. Insert and remove the dipstick without screwing it into the filler neck.  
Check the oil level shown on the dipstick.  
3. If the oil level is low, fill to the edge of the oil filler hole with the  
recommended oil (see page 26).  
4. Screw in the filler cap/dipstick securely.  
UPPER LIMIT  
FILLER CAP/DIPSTICK  
LOWER LIMIT  
Running the engine with a low oil level can cause engine damage.  
The Oil Alert system (applicable engine types) will automatically stop  
the engine before the oil level falls below safe limit. However, to avoid  
the inconvenience of an unexpected shutdown, always check the  
engine oil level before startup.  
24  
SERVICING YOUR ENGINE  
ENGINE OIL CHANGE  
Drain the used oil while the engine is warm. Warm oil drains quickly  
and completely.  
1. Place a suitable container below the engine to catch the used oil,  
then remove the filler cap/dipstick and the drain plug.  
2. Allow the used oil to drain completely, then reinstall the drain plug,  
and tighten it securely.  
Please dispose of used motor oil in a manner that is compatible with  
the environment. We suggest you take used oil in a sealed container  
to your local recycling center or service station for reclamation. Do  
not throw it in the trash, pour it on the ground, or down a drain.  
3. With the engine in a level position, fill to the outer edge of the oil  
filler hole with the recommended oil (see page 26).  
Engine oil capacity: 1.16 US qt (1.10 )  
Running the engine with a low oil level can cause engine damage.  
The Oil Alert system (applicable engine types) will automatically  
stop the engine before the oil level falls below the safe limit.  
However, to avoid the inconvenience of an unexpected shutdown,  
fill to the upper limit, and check the oil level regularly.  
4. Screw in the filler cap/dipstick securely.  
FILLER CAP/  
DIPSTICK  
OIL LEVEL  
DRAIN PLUG  
25  
SERVICING YOUR ENGINE  
ENGINE OIL RECOMMENDATIONS  
Oil is a major factor affecting performance and service life. Use  
4-stroke automotive detergent oil that is designed for engines  
operating on LPG.  
SAE 30 (API service classification SJ) is recommended for general use.  
The following are examples of oils that meet Honda’s requirements for  
LPG-fueled engines:  
Pennzoil HD 30  
Valvoline HPO 30  
Castrol HD 30  
For operation in temperatures below 32°F (0°C), 5W-30 synthetic oil  
may be used for easier starting. Do not use 5W-30 synthetic oil when  
the air temperature is above 32°F (0°C).  
Do not use multigrade mineral-based oils. The use of multigrade  
mineral-based oils may result in premature engine wear and/or  
damage.  
26  
SERVICING YOUR ENGINE  
AIR FILTER INSPECTION  
Remove the air cleaner cover and inspect the filter elements. Clean or  
replace dirty filter elements. Always replace damaged filter elements.  
Refer to page28 for instructions that apply to the air cleaner and filter  
service.  
PAPER  
FILTER  
ELEMENT  
FOAM  
FILTER  
ELEMENT  
27  
SERVICING YOUR ENGINE  
AIR CLEANER SERVICE  
A dirty air filter will restrict air flow to the carburetor, reducing engine  
performance. If you operate the engine in very dusty areas, clean the  
air filter more often than specified in the MAINTENANCE SCHEDULE.  
Operating the engine without an air filter, or with a damaged air filter,  
will allow dirt to enter the engine, causing rapid engine wear. This type  
of damage is not covered by the Distributor’s Limited Warranty.  
WING  
NUTS  
1. Remove the wing nut from the  
AIR  
CLEANER  
COVER  
air cleaner cover, and remove  
the cover.  
2. Remove the wing nut from the  
air filter, and remove the filter.  
3. Remove the foam filter from the  
paper filter.  
PAPER  
4. Inspect both air filter elements,  
and replace them if they are  
damaged. Always replace the  
paper air filter element at the  
scheduled interval (see page  
22).  
FILTER  
ELEMENT  
FOAM  
FILTER  
ELEMENT  
GASKET  
5. Clean the air filter elements if  
they are to be reused.  
28  
SERVICING YOUR ENGINE  
Paper air filter element: Tap the filter element several times on a hard  
surface to remove dirt, or blow compressed air [not exceeding 30 psi  
(207 kPa, 2.1 kgf/cm )] through the filter element from the inside.  
Never try to brush off dirt; brushing will force dirt into the fibers.  
Foam air filter element: Clean in warm soapy water, rinse, and allow to  
dry thoroughly. Or clean in nonflammable solvent and allow to dry.  
Dip the filter element in clean engine oil, then squeeze out all excess  
oil. The engine will smoke when started if too much oil is left in the  
foam.  
6. Wipe dirt from the inside of the air cleaner base and cover, using a  
moist rag. Be careful to prevent dirt from entering the air duct that  
leads to the carburetor.  
7. Place the foam air filter element over the paper element, and  
reinstall the assembled air filter. Be sure the gasket is in place  
beneath the air filter. Tighten the air filter wing nut securely.  
8. Install the air cleaner cover, and tighten the cover wing nut securely.  
29  
SERVICING YOUR ENGINE  
SPARK PLUG SERVICE  
Recommended spark plugs: BPR6ES (NGK)  
W20EPR-U (DENSO)  
An incorrect spark plug can cause engine damage.  
1. Disconnect the spark plug cap, and remove any dirt from around the  
spark plug area.  
2. Remove the spark plug with a 13/16-inch spark plug wrench.  
SPARK PLUG WRENCH  
3. Inspect the spark plug. Replace it  
if the electrodes are worn, or if the  
insulator is cracked or chipped.  
Clean the spark plug with a wire  
brush if you are going to reuse it.  
0.0280.031 in  
(0.700.80 mm)  
4. Measure the spark plug electrode  
gap with a suitable gauge. The  
gap should be 0.0280.031 in  
(0.700.80 mm). Correct the gap,  
if necessary, by carefully bending  
the side electrode.  
5. Install the spark plug carefully, by  
hand, to avoid cross-threading.  
30  
SERVICING YOUR ENGINE  
6. After the spark plug seats, tighten with a 13/16-inch spark plug  
wrench to compress the washer.  
If reinstalling the used spark plug, tighten 1/81/4 turn after the  
spark plug seats.  
If installing a new spark plug, tighten 1/2 turn after the spark plug  
seats.  
A loose spark plug can overheat and damage the engine.  
Overtightening the spark plug can damage the threads in the  
cylinder head.  
7. Attach the spark plug cap.  
IDLE SPEED ADJUSTMENT  
1. Start the engine outdoors, and allow it to warm up to operating  
temperature.  
2. Move the throttle lever to its slowest position.  
3. Turn the throttle stop screw to obtain the standard idle speed.  
200  
150  
Standard idle speed: 1,400  
rpm  
THROTTLE STOP SCREW  
31  
SERVICING YOUR ENGINE  
SPARK ARRESTER SERVICE (optional equipment)  
Your engine is not factory-equipped with a spark arrester. In some  
areas, it is illegal to operate an engine without a spark arrester. Check  
local laws and regulations. A spark arrester is available from  
authorized Honda servicing dealers.  
The spark arrester must be serviced every 100 hours to keep it  
functioning as designed.  
If the engine has been running, the muffler will be very hot. Allow the  
muffler to cool before servicing the spark arrester.  
1. Remove the two 8 mm nuts and remove the muffler from the  
cylinder.  
2. Remove the three 4 mm screws from the exhaust deflector, and  
remove the deflector.  
3. Remove the four 5 mm screws from the muffler protector and  
remove the muffler protector.  
4. Remove the 4 mm screws from the spark arrester, and remove the  
spark arrester from the muffler.  
5 mm SCREWS  
MUFFLER  
PROTECTOR  
EXHAUST  
DEFLECTOR  
4 mm SCREW  
4 mm  
SCREWS  
SPARK  
ARRESTER  
SPARK ARRESTER  
MUFFLER  
8 mm NUTS  
5. Use a brush to remove carbon deposits  
from the spark arrester screen. Be  
careful to avoid damaging the screen.  
The spark arrester must be free of  
breaks and holes. Replace the spark  
arrester if it is damaged.  
SCREEN  
6. Install the spark arrester, muffler protector, exhaust deflector, and  
muffler in the reverse order of disassembly.  
32  
HELPFUL TIPS & SUGGESTIONS  
STORING YOUR ENGINE  
Storage Preparation  
Proper storage preparation is essential for keeping your engine  
troublefree and looking good. The following steps will help to keep  
rust and corrosion from impairing your engine’s function and  
appearance, and will make the engine easier to start when you use it  
again.  
Cleaning  
If the engine has been running, allow it to cool for at least half an hour  
before cleaning. Clean all exterior surfaces, touch up any damaged  
paint, and coat other areas that may rust with a light film of oil.  
Using a garden hose or pressure washing equipment can force  
water into the air cleaner or muffler opening. Water in the air cleaner  
will soak the air filter, and water that passes through the air filter or  
muffler can enter the cylinder, causing damage.  
Water contacting a hot engine can cause damage. If the engine has  
been running, allow it to cool for at least half an hour before  
washing.  
33  
HELPFUL TIPS & SUGGESTIONS  
Engine Oil  
1. Change the engine oil (see page 25).  
Engine Cylinder  
1. Remove the spark plug (see page 30).  
2. Pour a tablespoon (510 cc) of clean engine oil into the cylinder.  
3. Pull the starter rope several times to disribute the oil in the cylinder.  
4. Reinstall the spark plug.  
5. Pull the starter rope slowly until resistance is felt and the notch on  
the starter pulley aligns with the hole at the top of the recoil starter  
cover. This will close the valves so moisture cannot enter the engine  
cylinder. Return the starter rope gently.  
Align notch on pulley  
with hole at top of cover.  
Storage Precautions  
Select a well-ventilated storage area away from any appliance that  
operates with a flame, such as a furnace, water heater, or clothes dryer.  
Also avoid any area with a spark-producing electric motor, or where  
power tools are operated.  
If possible, avoid storage areas with high humidity, because that  
promotes rust and corrosion.  
Leave the fuel valve lever in the OFF position at the source to reduce  
the possibility of fuel leakage.  
34  
HELPFUL TIPS & SUGGESTIONS  
Position the equipment so the engine is level. Tilting can cause oil  
leakage.  
With the engine and exhaust system cool, cover the engine to keep out  
dust. A hot engine and exhaust system can ignite or melt some  
materials. Do not use sheet plastic as a dust cover. A nonporous cover  
will trap moisture around the engine, promoting rust and corrosion.  
Removal From Storage  
Check your engine as described in the BEFORE OPERATION chapter of  
this manual.  
If the cylinder was coated with oil during storage preparation, the  
engine may smoke briefly at startup. This is normal.  
35  
HELPFUL TIPS & SUGGESTIONS  
TRANSPORTING  
If the engine has been running, allow it to cool for at least 15 minutes  
before loading the engine-powered equipment on the transport  
vehicle. A hot engine and exhaust system can burn you and can ignite  
some materials.  
Keep the engine level when transporting to reduce the possibility of  
fuel leakage. Turn the fuel valve OFF at the source.  
36  
TAKING CARE OF UNEXPECTED PROBLEMS  
ENGINE WILL NOT  
START  
1. Check control  
positions.  
Possible Cause  
Fuel valve OFF.  
Choke OPEN.  
Engine switch OFF.  
Correction  
OPEN valve.  
Move lever to CLOSED.  
Turn engine switch to  
ON.  
2. Check fuel.  
Out of fuel.  
Refuel.  
3. Remove and inspect  
spark plug.  
Spark plug faulty,  
fouled, or improperly  
gapped.  
Clean, gap, or replace  
spark plug (p. 30).  
Spark plug wet with  
fuel (flooded engine).  
Dry and reinstall spark  
plug. Start engine with  
throttle lever in FAST  
position.  
4. Take engine to an  
authorized Honda  
Carburetor malfunction,  
ignition malfunction,  
valves stuck, etc.  
Replace or repair faulty  
components as  
necessary.  
servicing dealer, or  
refer to shop manual.  
ENGINE LACKS  
POWER  
Possible Cause  
Correction  
1. Check air filter.  
Filter element(s)  
clogged.  
Carburetor malfunction,  
ignition malfunction,  
valves stuck, etc.  
Clean or replace filter  
element(s) (p. 28).  
Replace or repair faulty  
components as  
2. Take engine to an  
authorized Honda  
servicing dealer, or  
refer to shop manual.  
necessary.  
37  
TECHNICAL & CONSUMER INFORMATION  
TECHNICAL INFORMATION  
Serial Number Location  
SERIAL NUMBER  
& ENGINE TYPE  
Record the engine serial number in the space below. You will need this  
serial number when ordering parts, and when making technical or  
warranty inquires (see page 47 ).  
Engine serial number:  
38  
TECHNICAL & CONSUMER INFORMATION  
Remote Control Linkage  
The throttle and choke control levers are provided with holes for  
optional cable attachment. The following illustrations show  
installation examples for a solid wire cable and for a flexible, braided  
wire cable. If using a flexible, braided wire cable, add a return spring  
as shown.  
It is necessary to loosen the throttle lever friction nut when operating  
the throttle with a remotely-mounted control.  
REMOTE THROTTLE LINKAGE  
RETURN SPRING  
THROTTLE LEVER  
FRICTION NUT  
Flexible wire core  
mounting  
4 mm SCREW  
WIRE HOLDER  
OPTIONAL  
WIRE  
THROTTLE  
LEVER  
5 mm  
CIRCLIP  
Solid wire core  
mounting  
REMOTE CHOKE LINKAGE  
WIRE HOLDER  
CHOKE LEVER  
39  
TECHNICAL & CONSUMER INFORMATION  
Carburetor Modification for High Altitude Operation  
The GX270 and GX390 LPG-fueled engine do not require any  
modifications for high-altitude operation. However, performance will  
decrease at high altitudes.  
Fuel Regulator Information  
This engine is certified to comply with U.S. EPA and California ARB  
emission regulations using the Impco Beam regulator specified in the  
installation instructions (see below).  
Honda used this regulator and other specific parts and adjustments to  
demonstrate compliance with the emission regulations. Adjustable  
fuel system parts must have U.S. EPA and California ARB approved  
tamper resistant features to limit the available adjustment after the  
fuel system is correctly installed.  
If an equipment manufacturer did not install your engine in a product,  
you will need the installation instructions for the Honda certified  
system (see below).  
If you choose not to use the Honda fuel system, you must use a  
system that has been certified by the fuel system manufacturer to be  
used on this Honda engine.  
Or, if you use a fuel system that is not already certified, you must have  
certification test data satisfactory to the U.S. EPA or California ARB.  
The test data must prove the system will meet the emission standard  
both when the engine is new and at the end of its emission durability  
period (hours).  
To obtain a copy of the installation instructions for this engine, contact  
an independent Honda engine distributor, or our Customer Service  
Department (page 47 ).  
40  
TECHNICAL & CONSUMER INFORMATION  
Emission Control System Information  
Source of Emissions  
The combustion process produces carbon monoxide, oxides of  
nitrogen, and hydrocarbons. Control of hydrocarbons and oxides of  
nitrogen is very important because, under certain conditions, they  
react to form photochemical smog when subjected to sunlight. Carbon  
monoxide does not react in the same way, but it is toxic.  
Honda utilizes lean carburetor settings and other systems to reduce  
the emissions of carbon monoxide, oxides of nitrogen and  
hydrocarbons.  
The U.S. and California Clean Air Acts  
EPA and California regulations require all manufacturers to furnish  
written instructions describing the operation and maintenance of  
emission control systems.  
The following instructions and procedures must be followed in order  
to keep the emissions from your Honda engine within the emission  
standards.  
Tampering and Altering  
Tampering with or altering the emission control system may increase  
emissions beyond the legal limit. Among those acts that constitute  
tampering are:  
Removal or alteration of any part of the intake, fuel or exhaust  
systems.  
Altering or defeating the governor linkage or speed-adjusting  
mechanism to cause the engine to operate outside its design  
parameters.  
41  
TECHNICAL & CONSUMER INFORMATION  
Problems That May Affect Emissions  
If you are aware of any of the following symptoms, have your engine  
inspected and repaired by your servicing dealer.  
Hard starting or stalling after starting.  
Rough idle.  
Misfiring or backfiring under load.  
Afterburning (backfiring).  
Black exhaust smoke or high fuel consumption.  
Replacement Parts  
The emission control systems on your Honda engine were designed,  
built, and certified to conform with EPA and California emission  
regulations. We recommend the use of genuine Honda parts  
whenever you have maintenance done. These original-design  
replacement parts are manufactured to the same standards as the  
original parts, so you can be confident of their performance. The use  
of replacement parts that are not of the original design and quality  
may impair the effectiveness of your emission control system.  
A manufacturer of an aftermarket part assumes the responsibility that  
the part will not adversely affect emission performance. The  
manufacturer or rebuilder of the part must certify that use of the part  
will not result in a failure of the engine to comply with emission  
regulations.  
Maintenance  
Follow the maintenance schedule on page 22. Remember that this  
schedule is based on the assumption that your machine will be used  
for its designed purpose. Sustained high-load or high-temperature  
operation, or use in unusually wet or dusty conditions, will require  
more frequent service.  
42  
TECHNICAL & CONSUMER INFORMATION  
Air Index  
An Air Index Information hang tag/label is applied to engines certified  
to an emission durability time period in accordance with the  
requirements of the California Air Resources Board.  
The bar graph is intended to provide you, our customer, the ability to  
compare the emissions performance of available engines. The lower  
the Air Index, the less pollution.  
The durability description is intended to provide you with information  
relating to the engine’s emission durability period. The descriptive  
term indicates the useful-life period for the engine’s emission control  
system. See your Emission Control Warranty for additional  
information.  
Descriptive Term  
Moderate  
Applicable to Emissions Durability Period  
50 hours (065 cc)  
125 hours (greater than 65 cc)  
Intermediate  
Extended  
125 hours (065 cc)  
250 hours (greater than 65 cc)  
300 hours (065 cc)  
500 hours (greater than 65 cc)  
The Air Index Information hang tag must remain on the engine until it  
is sold. Remove the hang tag before operating the engine.  
43  
TECHNICAL & CONSUMER INFORMATION  
Specifications  
GX270  
15.7 × 16.9 × 16.0 in  
(400 × 430 × 407 mm)  
Length × Width × Height  
50.7 lbs (23.0 kg)  
Dry weight  
4-stroke, overhead valve, single cylinder  
16.5 cu-in (270 cm )  
Engine type  
Displacement  
[Bore × Stroke]  
Max. output  
[ 3.0 × 2.3 in (77 × 58 mm) ]  
8.9 bhp (6.6 kW, 9.0 PS) at 3,600 rpm  
14.1 lbf·ft (19.1 N·m, 1.95 kgf·m) at 2,500 rpm  
0.42 lb/hph (258 g/kWh, 190 g/PSh)  
Forced air  
Max. torque  
Fuel consumption  
Cooling system  
Ignition system  
PTO shaft rotation  
Transistorized magneto  
Counterclockwise  
GX390  
16.7 × 17.7 × 17.4 in  
(425 × 450 × 443 mm)  
Length × Width × Height  
63.9 lbs (29.0 kg)  
Dry weight  
4-stroke, overhead valve, single cylinder  
23.7 cu-in (389 cm )  
Engine type  
Displacement  
[Bore × Stroke]  
Max. output  
[ 3.5 × 2.5 in (88 × 64 mm) ]  
12.9 bhp (9.6 kW, 13.0 PS) at 3,600 rpm  
19.5 lbf·ft (26.5 N·m, 2.7 kgf·m) at 2,500 rpm  
0.42 lb/hph (258 g/kWh, 190 g/PSh)  
Forced air  
Max. torque  
Fuel consumption  
Cooling system  
Ignition system  
PTO shaft rotation  
Transistorized magneto  
Counterclockwise  
GX270/GX390 Tuneup  
ITEM  
Spark plug gap  
SPECIFICATION  
0.0280.031 in  
MAINTENANCE  
Refer to page: 30  
(0.700.80 mm)  
IN: 0.15 ± 0.02 mm(cold)  
EX: 0.20 ± 0.02 mm(cold)  
Valve clearance  
See your authorized  
Honda dealer  
No other adjustments needed.  
Other specifications  
44  
TECHNICAL & CONSUMER INFORMATION  
Wiring Diagram  
Engine Types With Oil Alert  
45  
TECHNICAL & CONSUMER INFORMATION  
CONSUMER INFORMATION  
Honda Publications  
These publications will give you additional information for  
maintaining and repairing your engine. You may order them from  
your Honda engine dealer.  
Shop Manual  
This manual covers complete maintenance and overhaul procedures.  
It is intended to be used by a skilled technician.  
Parts Catalog  
This manual provides complete, illustrated parts lists.  
46  
TECHNICAL & CONSUMER INFORMATION  
Warranty Service Information  
Servicing dealership personnel are trained professionals. They should  
be able to answer any question you may have. If you encounter a  
problem that your dealer does not solve to your satisfaction, please  
discuss it with the dealership’s management. The Service Manager or  
General Manager can help. Almost all problems are solved in this way.  
If you are dissatisfied with the decision made by the dealership’s  
management, contact the Honda Power Equipment Customer  
Relations Office. You can write to:  
American Honda Motor Co., Inc.  
Power Equipment Division  
Customer Relations Office  
4900 Marconi Drive  
Alpharetta, Georgia 30005-8847  
Or telephone: (770) 497-6400  
When you write or call, please give us this information:  
Model and serial number (see page 38 )  
Name of dealer who sold the engine to you  
Name and address of dealer who services your engine  
Date of purchase  
Your name, address and telephone number  
A detailed description of the problem  
47  
MEMO  
48  
QUICK REFERENCE INFORMATION  
Fuel  
Type  
Type  
LPG with a propane content of  
95 % or higher (page 23)  
SAE 30, API SJ, for general use  
(page 26)  
Engine Oil  
Capacity  
Type  
1.16 US qt (1.10 )  
Spark Plug  
NGK: BPR6ES ,  
DENSO: W20EPR-U  
Gap  
0.0280.031 in (0.700.80 mm)  
(page 30)  
200  
Carburetor  
Maintenance  
Idle speed  
Before  
each use  
First 20  
hours  
Subsequent  
1,400  
rpm (page 31)  
150  
Check engine oil level.  
Check air filter.  
Change engine oil.  
Refer to the maintenance  
schedule on page 22.  
K1:GX390  
300.2003.10  
A H  
N
H C  
31ZK6601  
00X31-ZK6-6010  
EM3  
Printed in Japan  

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