How to Adjust the Carburator on a Chainsaw


There are three adjustments on a chainsaw carburetor under the plastic housing. The adjustments control the idle speed when the chain does not operate, the low speed of the chainsaw motor and the motor’s high speed. Correct adjustments of all three screws allow a chainsaw to run evenly when it idles without dying and needing restarting, a correct gas to air mixture and a high speed when cutting so the saw does not bind in wood.

Things You'll Need

  • Adjustable wrench
  • Small flat screwdriver
  • Compressed air
  • Place an adjustable wrench on each bolt on the chainsaw housing. Turn each bolt counterclockwise to loosen and remove all bolts. Generally, two to four bolts hold the protective plastic housing over the motor and the carburetor. Remove each housing piece and set it aside.

  • Start the chainsaw engine and let it idle for five minutes to warm the motor.

  • Blow off any dust or debris from the engine and carburetor area with canned compressed air or an air compressor.

  • Place a small flat screwdriver on the idle adjustment screw. This is the top screw on the back of the motor. Turn the screw counterclockwise to increase the idle to full force. The chainsaw clutch will engage and start turning the chain. Turn the screw clockwise until achieving the highest idle possible without the clutch engaging.

  • Place a small flat screwdriver on the low speed adjustment screw on the bottom left side of the motor. Turn the screw counterclockwise until the motor sputters and make a mental note of the screw position. Turn the screw clockwise until the motor sputters or runs roughly and note the screw position. Turn the screw counterclockwise in between the two rough running areas to maintain an even idle speed.

  • Squeeze the throttle trigger entirely to the chainsaw handle. The motor should run without missing. Place a small flat screwdriver o the high-speed adjustment screw on the bottom right side of the motor to adjust full throttle speed. Turn the screw counterclockwise to run faster or clockwise to run slower while an even sound with slight roughness emits from the motor.

  • Turn the chainsaw off.

  • Replace the housing and tighten the bolts with an adjustable wrench in a clockwise direction.

Tips & Warnings

  • The idle adjustment is set in the highest speed possible without the clutch engaging so when in use the chainsaw will idle while adjusting wood for cutting without dying.
  • The low speed adjustment screw controls the air to fuel ratio on chainsaws. Turning it clockwise reduces the amount of fuel and makes the engine run lean and sputter. Turning the screw counterclockwise produces a rich running chainsaw while adding extra fuel to the ratio.
  • The high-speed adjustment screw controls the chainsaw while the trigger is squeezed with the clutch engaging and cutting wood. The high speed should sound as close to running smooth with a slight rough sound.
  • Place the chainsaw on a table or workbench with the chain and bar off the edge of the surface to make adjustments. This prevents the clutch engaging, turning the chain and cutting the surface.

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  • Photo Credit Chain saw against firewood pile image by Andrzej Thiel from
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