How to Adjust the Needle on a Walbro Chain Saw Carburetor

Disconnect the gas cap and drain all remaining fuel into an approved container. Mix up a fresh batch of chain saw fuel, following your product’s fuel mixing instructions. Fill the tank at least three-quarters full with the gasoline.

Unscrew the top cover that sits above the carburetor and cylinder. Unhook the air filter from the engine. Brush off the air filter, the housing, and the area around the carburetor and cylinder fins. Fit the parts back together.

Set the chain saw in an open area where the chain won’t hit anything during adjustment. Start the chain saw and give it a few minutes to warm up.

Locate the idle adjustment screw for your Walbro carburetor. On most saws, this will be on the right side of the carburetor, accessible via a small hole in the clutch cover. Insert the small screwdriver into the idle hole.

Rotate the screw slowly clockwise so that the engine starts to speed up and the chain begins to spin on its own. Turn the screw back slowly counterclockwise until the chain stops spinning. Adjust the idle speed to the highest rpm before the chain starts spinning.

Locate the low-speed adjustment screw, usually just above the idle screw hole. Insert the screwdriver and turn the screw slowly clockwise until the engine speeds up. Turn the screw counterclockwise until the engine slows down and starts bubbling.

Adjust the low-speed screw up and down slowly to locate the best low speed. Listen for a clean, smooth sound from the engine. Test the acceleration to the high speed; if it’s sluggish, increase the low speed by turning the screw clockwise in 1/8 increments. Readjust the idle speed once the low speed has been set.