How To Adjust A Stihl Chainsaw Carburetor

Stihl Chainsaw Carburetor adjustment

Stihl Chainsaw Carburetor Adjustment

All Stihl chainsaws have just three carburetor adjustment screws, so fairly easy to work on when you need to a Stihl Chainsaw Carburetor adjustment.

(LA) Idle Speed screw – This controls the engine speed at idle. If set too low, the saw will die. If set too high the chain will run. This is dangerous.

(L) Low speed adjustment screw – This is the low speed jet. This is the adjustment that controls the air/fuel mixture at idle. Adjust this screw too rich and the chainsaw will blubber and die at idle speed. Adjust this screw too lean and the engine will starve. The saw will race or surge. An extremely lean adjustment will also cause the engine to die.

(H) High speed adjustment screw – This is the high speed jet. This is the adjustment that controls the air/fuel mixture at high RPMs. Adjust this screw too rich and the chainsaw will blubber, too lean and it will over rev.

Safe Basic Settings

Screws (H) & (L) – Turn the adjustment Screws (H) & (L) down onto their seats (clockwise). Back them off 1 complete turn (counter-clockwise)
Screw (LA) – Turn (LA) Idle Speed screw until the chain stops. Then turn counter-clockwise one quarter of a turn.

Fine Tuning – Screw (L)

Erratic idling behavior; poor acceleration – Idle setting too lean; turn low speed adjusting screw (L) counterclockwise until engine runs and accelerates smoothly. Readjust screw (LA).

Exhaust smokes at idle speed –Idle speed setting too rich; turn low speed adjusting screw (L) clockwise until engine speed drops. Then turn screw back one quarter turn and check that engine still accelerates smoothly when you open the throttle. Readjust screw (LA).

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