Things You'll Need
Wire coat hanger
Replacement fuel filter
A chainsaw carburetor needs to be adjusted so that the chain does not move when the saw is idling. Problems with chainsaw carburetors are usually related to the fuel and air mix ratio. This can be fixed with some simple adjustments. The idle speed can be adjusted if it’s too high or too low. Other fixes can include replacing the fuel filter. Troubleshooting a carburetor also involves taking a look at the altitude at which you are using the chainsaw.
Replace the fuel filter if the engine cranks but doesn’t start. The fuel may not be getting to the carburetor. Pull the fuel filter out of the gasoline tank. You can use a piece of coat hanger wire to do this. If the filter is dirty, replace it. Pull the old one off the tube and insert the new one.
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Consult a topographic map to determine your altitude. Adjust the idle speed if you are operating the chainsaw over 1,100 feet above sea level.
Adjust the idle speed. Adjust it with the carburetor adjustment screw if the engine idles too fast or too slowly, or the chain moves on idle. Start the engine and run it for a few minutes to bring it up to the correct operating temperature. Open the choke quickly twice. This removes air from the system. Stop the engine. Turn the high-speed adjustment screw anti-clockwise until it stops. Turn the low-speed adjustment screw halfway between full clockwise stop and anti-clockwise stop. The adjustment screws will be near the rope starter pull and on the side of the engine. They will be marked “H” and “L” or in a similar fashion. Start the engine and turn the idle speed adjustment screw clockwise until the chain begins to move. Turn the screw anti-clockwise until the chain stops. Keep turning the screw a further quarter turn.
Check for a smooth acceleration from idle to high speed. Open the throttle fully for a few seconds to clear fuel and then idle the chainsaw. Turn the low-speed adjustment screw anti-clockwise an eighth of a turn if you experience hesitation accelerating.
Don’t forget to readjust the carburetor if you want to use the chainsaw below 1,100 feet.