Honda GX640 Troubleshooting
| Engine Model: Honda GX640 |
| Engine Type: 4-cycle two-cylinder OHV liquid-cooled gasoline |
| Total Displacement: 38.7 cu.in (635 cc) |
| Rated Engine Power: 20 Hp (14.7 kW) at 3600 rpm |
| Carburetor Type: Horizontal with butterfly valve |
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| Engine starts up hard or won't start |
Empty fuel tank - Add fuel.
Wrong grade of gasoline - Use correct fuel grade.
There is air in the fuel system - Bleed the system.
Spark plug wire is loose or disconnected - Check the spark plug wire connection, repair or replace.
Spark plug is damaged - Change spark plug.
Plugged fuel filter - Change fuel filter.
Faulty safety switch - Change damaged switch.
Carburetor incorrectly set - Set carb correctly.
Bad compression - Check and change damaged parts.
Choke cable is not adjusted properly or worn - Replace cable or adjust properly.
Air intake screen is plugged - Wash or clean as required.
Ignition system problems - Inspect ignition system and change faulty parts.
Throttle cable is stuck or faulty - Replace or clean the cable.
Air filter element is clogged - Replace or service air filter.
Clogged or defective fuel pump - Service or change fuel pump.
| Engine starts and stops suddenly |
Damaged spark plug - Install new spark plug.
Dirty or defective carburetor - Service or replace carburetor.
Ignition coil is defective - Change ignition coil as required.
Loose or worn valve springs - Replace valve springs.
Valves are stuck - Valves must be cleaned.
Not enough engine oil - Fill the crankcase with engine oil.
Engine is running overloaded - Reduce engine load.
Clogged cooling fins - Need to wash or clean.
Carburetor fuel mixture is too lean - Make the correct settings.
Improper ignition timing - Set the ignition timing properly.
Improper valve setting - Valves needs to be adjusted properly.
Stale gasoline - Use proper gasoline.
Engine is overloaded - Reduce the load.
Insufficient engine oil - Fill the crankcase with engine oil.
Low idle speed adjustment is incorrect - Correct idle settings.
Fuel pump is faulty or clogged - Check fuel pump and replace if necessary.
Crankshaft or main bearings wear - Worn parts replacement required.
Valve clearance is not correct - Adjust valve clearance.
Piston rings or cylinder bore are worn - Replace defective components.
Carburetor is improperly adjusted or dirty - Adjust the carburetor correctly or clean it.
Dirty air filter element - Change or clean air filter.
Fuel pump is defective or dirty - Clean or install new fuel pump.
Defective ignition - Check ignition and replace faulty components.
Damaged cylinder-head gasket - Change cylinder head gasket.
Stuck or burned valves - Change or clean valves.
Push rod is bent or worn - Push rod needs to be changed.
Damaged cylinder block components - Defective parts need to be replaced.
Oil filter element is plugged (if equipped) - Clean or change oil filter.
| Engine uses too much fuel |
Throttle did not open fully - Replace or adjust throttle cable.
Incorrect adjustment of carburetor main jet - Adjust main jet as required.
Faulty or loose spark plug - Replace or tighten spark plug.
Valves are worn, burned or stuck - Replace or clean valves.
Sleeve, piston, or rings are damaged - Replace defective parts.
Excessive valve clearance - Adjust valve clearance.
| Excessive engine oil consumption |
Worn gaskets or seals - Replace to repair leaks.
Valve stems and guides are worn - Install new valves.
Piston rings are stuck or broken - Have piston rings replaced.
Cylinder liner or piston is scored - Check liner and piston, change as required.
Breather pipe or hose is clogged - Clean or replace.
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