Honda GX390 Troubleshooting
| Engine Model: Honda GX390 |
| Engine Type: 4-cycle 1-cylinder OHV horizontal shaft air-cooled gasoline |
| Total Displacement: 21.9 cu.in (359 cc) |
| Rated Engine Power: 13 Hp (9.6 kW) at 3600 rpm |
| Carburetor Type: Horizonal with butterfly valve |
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| Engine hard starting or not starting |
Empty fuel tank - Fill fuel up.
Wrong grade of gasoline - Use quality fuel.
Dirty fuel system - Check and clean.
Spark plug wire is disconnected or loose - Check the spark plug wire connection, repair or replace.
Spark plug is defective - Spark plug need to be replaced.
Fuel filter is dirty - Install new filter.
Faulty safety switch - Change damaged switch.
Carburetor settings incorrect - Adjusting as required.
Bad compression - Check and change damaged parts.
Throttle cable is worn or adjusted improperly - Change cable or adjust properly.
Clogged cooling fins - Wash or clean as required.
Defective ignition - Check ignition system and replace faulty parts.
Choke cable is faulty or stuck - Service or replace the cable.
Clogged air filter - Change or service air filter.
Fuel pump is defective or dirty - Clean or install new fuel pump.
| Engine starts but then stops |
Faulty spark plug - Change spark plug.
Defective or clogged carburetor - Clean or change carburetor.
Ignition coil is defective - Ignition coil must be replaced.
Broken or bad valve springs - Replace valve springs.
Valves sticking - Clean the valves.
Engine oil level is low - Check oil level and add oil as required.
Excessive engine load - Reduce load.
Air intake screen is plugged - Need to clean or wash.
Too lean fuel mixture in carburetor - Adjust carburetor properly.
Ignition timing is wrong - Set the ignition timing correctly.
Valve setting is improper - Adjust valves correctly.
Stale gasoline - Use correct fuel.
Engine is under excessive load - Reduce engine load.
Insufficient engine oil - Fill up the engine oil.
Low idle speed adjustment is incorrect - Correct idle settings.
Clogged or damaged fuel pump - Service or change fuel pump.
Main bearings or crankshaft are worn out - Need to install new components.
Excessive valve clearance - Check and adjust.
Worn piston rings or cylinder bore - Change faulty components.
Clogged or incorrectly adjusted carburetor - Adjust the carburetor correctly or clean it.
Dirty air filter element - Service or replace air filter.
Fuel pump is faulty or clogged - Clean or install new fuel pump.
Ignition system problems - Check ignition and replace faulty components.
Blown cylinder head gasket - Install new cylinder head gasket.
Valves are burned or stuck - Service or change valves.
Damaged or worn push rod - Push rod should be replaced.
Cylinder block parts are faulty - Replace defective parts as required.
Oil filter element is plugged (if equipped) - Service or change oil filter.
| Engine using too much gasoline |
Throttle does not open well - Inspect throttle cable and adjust it.
Carburetor main jet adjustment is incorrect - Adjust the carburetor main jet correctly.
Loose or defective spark plug - Tighten or change the spark plug.
Stuck, burned, or worn valves - Replace or clean valves.
Worn sleeve, rings, or piston - Replace defective components.
Valve clearance is wrong - Adjustment procedure required.
| Engine using too much oil |
Worn gaskets or seals - Worn parts need to be replaced.
Damaged valve guides or valve stems - Valves replacement required.
Stuck or defective piston rings - Change the piston rings as required.
Worn piston or cylinder liner - Inspect liner and piston, change as necessary.
Breather hose or pipe is plugged - Replace or service.
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