Honda GC135 Maintenance Guide

gc-135The GC135 may be small, but this Honda engine is used in a wide range of equipment by a large number of manufacturers. Whether your motor powers a pressure washer or a pump, this guide will help you keep it powering your equipment for years to come.


Always let the engine cool before servicing it, especially when working around the muffler: it can still be hot up to a half hour after the engine has been used.

While it may be easier to work on the engine inside, running the motor in an enclosed space can lead to carbon monoxide buildup which can be lethal. Always move the engine outside away from buildings before starting.

Maintenance Schedule

Before each use: Check the oil level and air filter.
First month or 5 hours of operation: Change the oil
Every three months or 25 hours: Clean the air filter. If using the engine in areas with high temperatures or under constant heavy load, change the oil.
Every 6 months or 50 hours: Change the oil
Every year or 100 hours: Check the spark plug and clean the spark arrester (if installed.)
Every two years or 250 hours: Replace the air filter and spark plug. Check the fuel line and replace if it shows signs of cracking.

Honda recommends bringing this motor in for service every year or 100 hours to have the valve clearance and idle speed checked as well as having the fuel tank and filter cleaned. A professional should also clean the combustion chamber every 250 hours.


Honda recommends fresh unleaded gasoline with an octane rating of at least 86. Always add fuel with the engine off, and never fill the tank past the fuel level mark, visible inside the filler neck. A little pinging is normal under heavy loads, but if it’s persistent, switch to a different gasoline.


The GC135 holds 0.61 quarts (0.58 liters) of oil. The maximum oil level is at the top of the filler neck when the engine is sitting level. Honda recommends oil that is API service category SJ or later. 10W30 should be used for most operating temperatures, but 5W30 can be used below 32°F (0°C) and SAE 30 at temperatures above 50°F (10°C.) Some versions of this engine have the Oil Alert system which will shut down the motor automatically if the oil level is too low. While this will prevent internal damage, it’s still a good idea to inspect the oil level periodically.

To check the oil, remove the filler cap/dipstick, wipe it clean, and reinsert it into the filler neck without screwing it back in. Pull it back out: if there isn’t anything on it, add oil.

To change the oil, remove the filler cap/dipstick and place a drain pan under the motor. Remove the drain plug and washer, located at the base of the engine near the filler neck. Once drained, reinstall the plug and washer and add oil through the filler neck. Screw the dipstick back into the engine.

Air Filter

To access the filter, push in the two tabs on the housing, located on the side by the fuel tank, and flip up the cover.

If the filter needs to be cleaned, remove it from the engine and tap it against a hard surface or use compressed air with a maximum pressure of 30 psi to blow out the filter medium. Wipe out the inside of the air cleaner housing before reinstalling the filter.

Spark Plug

To access the spark plug, disconnect the plug cap and remove the plug with a 13/16 inch spark plug wrench or socket.

The spark plug gap should be set to 0.028-0.031 inches (0.70-0.80 mm.) Replace the plug if the electrode is worn or the insulator is damaged.

Thread the plug back into the engine by hand. Once seated, use the wrench or socket to turn it another 1/8-1/4 turn to ensure it’s seated. If you’re installing a new plug, tighten 1/2 turn to ensure a good seal with the new spark plug washer. Reattach the spark plug cap.

Spark Arrester (if Equipped)

A spark arrester isn’t installed at the factory, but it can be added to any GC135 to meet local fire safety laws.

To access the spark arrester, remove the muffler protector by unscrewing three 6mm bolts, then remove the screw holding the arrester in place. Slide the arrester out of the muffler. Reinstall in reverse order.

To clean the arrester, use a wire brush to remove any carbon build-up. Replace the arrester if it has holes or cracks.

Getting Parts for the GC135

If you need parts for your Honda motor, visit We’re a certified dealer for all Honda small engine equipment, and we can ship the parts you need anywhere in the U.S. and Canada. Finding parts is easy, too, thanks to our advanced search engine with factory parts diagrams and descriptions that let you match up exactly what you’re ordering with what you need to replace.

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