How to Adjust a Chainsaw Carburetor With a Tachometer

Unscrew the air filter cover, usually on the top of most chainsaws. Remove the air filter and clean it according to your model's specifications. Brush off the area around the air filter and the air filter cover.

Unscrew the chainsaw's fuel tank and dump out any old fuel into the fuel container. Fill the tank at least three-quarters full with freshly mixed chainsaw fuel. Start the chainsaw engine in a place where the chain won't contact anything during carburetor adjustment. Let the chainsaw warm up for at least 10 minutes.

Connect the tachometer to the chainsaw, according to your tachometer's specifications, or hold it close enough to the cylinder for it to get an accurate reading. Locate the three carburetor adjusting screws on your chainsaw's carburetor.

Set the idle speed on your chainsaw's carburetor, inserting the small screwdriver into the hole marked for the idle speed. Turn the screw clockwise until the chain starts spinning and check the reading on the tachometer. Adjust the screw clockwise or counterclockwise to reach your chainsaw's required idle speed.

Set the low speed on your chainsaw's carburetor, inserting the small screwdriver into the hole marked for the low speed. Turn the screw in clockwise until the engine speeds up and note the reading on the tachometer. Adjust the screw as necessary until the low speed reaches your chainsaw's necessary low speed.

Readjust the idle speed screw once the low speed screw is set, as it will likely have changed.