How to Adjust the Walbro Chainsaw Carburetor

Unscrew the top air filter cover on the chainsaw. Take off the cover, remove the air filter and clean it according to the manufacturer's specifications. Replace the air filter if it can't be cleaned.

Unscrew the fuel cap on the chainsaw and drain all old fuel into an approved fuel container. Fill the fuel tank at least 3/4-full with the freshly mixed two-cycle engine fuel. Start the chainsaw's engine and allow it to warm up for at least 10 minutes.

Place the chainsaw in an area so that the chain won't contact anything during this procedure. Locate the carburetor adjusting screws on the Walbro carburetor. Insert the small screwdriver into the hole marked for the idle speed.

Rotate the screw slowly clockwise until the engine speeds up and the chain starts moving. Rotate the screw counterclockwise until the chain stops moving. Find the highest permissible rpm before the chain begins turning.

Insert the small screwdriver into the hole marked for the carburetor's low speed. Turn the screw slowly clockwise until the engine speeds up and starts surging. Turn the screw back counterclockwise until the engine slows down and starts bubbling.

Fine-tune the low speed in between the faster and slower settings. Locate the point where the engine sounds clean and smooth, while still accelerating properly. Don't over-adjust this screw. Adjust the idle speed again after locating the low speed setting.