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How to Adjust the Carburetor on a Stihl 066 Chainsaw

Kenneth Crawford

The Stihl 066 chainsaw is a convenient tool for homeowners with trees and large shrubbery requiring regular maintenance. One way to ensure the chainsaw is operating at peak efficiency is to adjust the carburetor. Adjusting the carburetor on a Stihl 066 chainsaw involves three separate adjustments. Care should be taken when adjusting not to lean out the mixture causing the engine to operate at higher than normal speeds. The high and low speed adjustments are not usually necessary. Often a simple adjustment of the idle is all you need.

  1. Place the Stihl 066 chainsaw on the ground and start it as you would normally. Allow the engine to warm up for five minutes before attempting any carburetor adjustments. Locate the carburetor adjustment screws on the back of the chainsaw. There are three screws. One with "H' stamp, one with a "L" stamp and one with an "LA" stamp.

  2. Turn the "LA" screw clockwise with a flat-head screwdriver just until the chain begins to rotate on the chainbar. Turn the screw counterclockwise until the chain stops moving. This is the idle and the chainsaw should stay at this speed without sputtering or the chain moving.

  3. Adjust the "L" low speed screw clockwise with the screwdriver until the engine begins to make a low gurgling sound. Turn the screw ¼ turn counterclockwise.

  4. Squeeze the trigger on the chainsaw. The throttle should gradually raise the engine speed without hesitation or smoking. Turn the "H" high speed adjustment screw clockwise until the exhaust begins to smoke slightly.

  5. Turn the screw counterclockwise until the engine begins to sputter while under full throttle. Turn the screw to the midway point between sputtering and exhaust smoke. Readjust the idle if necessary.