The Honda GX240 is a 0.24 L 1-cylinder natural engine rated at 3600 rpm. It powers generator sets from Honda, including the EG3500X and EM3800SX. It holds 1.1 L (0.3 gal) of oil.
Maintenance schedule
| Item | Spec | Capacity | Part # | Interval | |
|---|
| Air filter | Wash in household detergent and warm water or nonflammable/high flash point solvent, dry, soak in clean engine oil and squeeze out excess | | — | 3 hr | |
| Fuel filter | | | — | 50 hr | |
| Oil | Honda 4-stroke oil or equivalent high detergent premium quality motor oil, Service Classification SE or SF; SAE 10W-40 recommended for general all-temperature use | 1.1 l | — | 20 hr | |
| Spark plug | BPR5ES (NGK) / W16EPR-U (ND) | | — | 500 hr | |
Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.
Procedures
12Setting up 10 sec start delay adjustment
⚠ 10 sec start delay is used in combination with an ATS panel to prevent multiple short start-stop commands coming from the ATS panel while the mains is unstable during blackout.
- Open the controller cover and locate the red dip switch (S-DELAY).
- Use your finger to move the dip switch 1 to ON position.
- Replace the cover and tighten screws.
Air Cleaner Service maintenance
⚠ Never use gasoline or low flash point solvents to clean the element.
⚠ Never run the generator without the air cleaner.
- Remove wing nut and air cleaner cover; remove and separate elements.
- Check both elements for holes or tears; replace if damaged.
- Foam element: wash, rinse and dry thoroughly, soak in clean engine oil, squeeze out excess.
- Paper element: tap lightly on hard surface or blow compressed air from inside out.
Changing Oil maintenance
⚠ Used motor oil may cause skin cancer if repeatedly left in contact with skin.
- Drain oil while engine is still warm.
- Remove drain plug and filler cap, drain oil, retighten plug securely.
- Refill with recommended oil and check level.
Engine Oil Change maintenance
⚠ Wash hands with soap after handling used oil.
- Remove drain plug and sealing washer, remove oil filler cap, and drain oil.
- Reinstall drain plug and sealing washer. Tighten securely.
- Refill with recommended oil and check oil level.
Fuel Sediment Cup Cleaning maintenance
- Turn fuel valve OFF. Remove sediment cup, O-ring, and filter.
- Clean sediment cup, O-ring, and filter in nonflammable solvent.
- Reinstall filter, O-ring, and sediment cup.
- Turn fuel valve ON and check for leaks.
Pre-operation Engine Oil Check maintenance
⚠ Running the engine with insufficient oil can cause serious engine damage.
- Check engine on a level surface with engine stopped.
- Remove oil filler cap and wipe dipstick clean.
- Insert dipstick into oil filler neck but do not screw it in.
- If level is low, fill to top of oil filler neck.
Refueling maintenance
⚠ Gasoline is extremely flammable and explosive; refuel with engine stopped in a well ventilated area.
⚠ Do not smoke or allow flames or sparks.
⚠ Do not overfill; wipe up spilled fuel before starting.
- Check the fuel level.
- If low, fill to the shoulder of the fuel filter.
- Close filler cap securely.
Sediment Cup Cleaning maintenance
- Turn the fuel valve to OFF.
- Remove the sediment cup and O-ring and wash in nonflammable solvent.
- Dry thoroughly and reinstall securely.
- Turn fuel valve ON and check for leaks.
Spark Arrester Maintenance maintenance
⚠ Allow muffler to cool before proceeding.
⚠ Be careful not to damage the spark arrester screen.
Tools: brush
- Remove eight 5 mm screws from muffler protector and remove protector.
- Remove 4 mm screw from spark arrester and remove it from muffler.
- Use a brush to remove carbon deposits from the arrester screen.
- Install arrester and muffler in reverse order of disassembly.
Spark Plug Service maintenance
⚠ Muffler will be very hot if engine has been running.
⚠ Never use a spark plug of incorrect heat range.
Tools: spark plug wrench, feeler gauge, wire brush
- Remove spark plug cap and use spark plug wrench to remove plug.
- Visually inspect plug; discard if insulator cracked or chipped.
- Measure plug gap with feeler gauge.
- Check washer condition and thread plug in by hand.
- Tighten with spark plug wrench to compress washer.
Storage Preparation maintenance
⚠ Turn engine switch and oil alert switch OFF and keep generator level when transporting.
- Ensure storage area is free of excessive humidity and dust.
- Drain fuel: remove and empty sediment cup with fuel valve OFF.
- Turn fuel valve ON and drain tank into suitable container.
- Replace sediment cup and tighten securely.
- Loosen carburetor drain screw and drain gasoline.
- Change the engine oil.
- Remove spark plug, pour about a tablespoon of clean engine oil into cylinder, crank several revolutions, reinstall plug.
- Pull starter rope slowly until notch on pulley aligns with hole on recoil starter, then cover engine.
Storage Procedure maintenance
⚠ Gasoline is extremely flammable. Perform in well-ventilated area with engine stopped.
- Drain carburetor by loosening drain screw into suitable container.
- Change engine oil.
- Remove spark plug, pour about a tablespoon of clean engine oil into cylinder. Crank engine several revolutions, reinstall spark plug.
- Slowly pull starter grip until resistance is felt.
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
Common questions
What is the oil capacity of the Honda GX240?
The Honda GX240 engine has an oil capacity of 1.1 liters.
What is the displacement of the Honda GX240?
The Honda GX240 has a displacement of 0.242 liters with 1 cylinders.
Which generators use the Honda GX240 engine?
The Honda GX240 powers 2 generator set(s), including Honda EG3500X, Honda EM3800SX.
How often should you change the oil in the Honda GX240?
The Honda GX240 oil change interval is every 20 hours.
What is a common problem with the Honda GX240 engine?
A commonly reported issue on generators using the Honda GX240 is: Running the engine with persistent spark knock or pinging can cause engine damage.. Fix: Running the engine with persistent spark knock or pinging is misuse, and the Distributor’s Limited Warranty does not cover parts damaged by misuse..