How to Tune a Carburetor on a Stihl 066

The Stihl 066 chainsaw comes factory-made with a preset carburetor. When a carburetor is working properly, the saw will idle while the blade stays stationary, it revs up smoothly without hesitation, and it will cut without stalling. If your chainsaw begins to not function in this fashion, it's advisable to adjust the carburetor back to the factory presets.

Carburetor cleaner
Small flathead screwdriver.

Instructions

- 1
  Set the chainsaw on level ground. Remove the air filter cover connected to the carburetor that is bolted to the engine block. Remove and inspect the air filter. Clean or replace it, and then reinstall the air filter cover.
- 2
  Clean the spark arrestor screen at the exhaust port on the muffler; it's attached by two small screws. Spray it with carburetor cleaner until you can see through all the holes in the screen, and then reattach the screen.
- 3
  Adjust the carburetor. There are three adjustment screws on the side of the carburetor that are marked on the chainsaw housing. One is marked with an "L" and it controls the low speed when the chainsaw is idling. Start the chainsaw, turn the "L" screw clockwise until it hits the stop, and then back it off one quarter turn.
- 4
  Adjust the "H" screw that controls the high speed. Advance the saw to the full throttle position. Turn the "H" screw counterclockwise until it hits the stop. Back it off in quarter-inch increments up to three-quarters of a turn until the engine runs smoothly.
- 5
  Adjust the "LA" screw if the chain is turning while in idle. Turn the screw counterclockwise until the chain stops turning.

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