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How to Adjust the Carburetor of a Weedeater SST25

The Weedeater SST25 is an occasional use trimmer. It is not built for heavy trimming operations. The only adjustments that the owner can perform on the carburetor is the idle adjustment. Sometimes a simple cleaning of the air filter will resolve any problems that resemble carburetor issues. You will need to adjust the idle speed from time to time. The trimmer should run smoothly while idling and the trimmer head should not rotate.

Locate the idle adjustment screw on your trimmer. The idle adjustment screw is between the air filter cover and the engine body. You will be adjusting the screw from the front of the engine.

Place the trimmer on a work bench so that the trimmer head can spin freely without touching anything. You should be able to start the engine and stay away from the rotating trimmer head.

Start the trimmer and run the engine at high idle for two minutes to allow the engine time to warm up. Squeeze the throttle trigger to allow the engine to come to its normal idle.

Observe the trimmer head while the engine is idling. The trimmer head should not turn and the engine should stay running. If the trimmer stalls or stops running, turn the idle adjustment screw clockwise with a flathead screwdriver. Turn the screw in small 1.8-turn increments. Restart the engine and continue adjusting the screw until the engine does not stall.

Turn the idle adjustment screw counter-clockwise if the trimmer head is rotating while the engine idles. Continue turning the screw counter-clockwise until the trimmer head does not rotate and the engine stays running.

Adjust The Carburetor On A Lawn Boy

A dead give-away that you need to adjust the carburetor on your Lawn-Boy mower is excessive gas consumption or black smoke when the mower is in operation. Locate the carburetor on your Lawn-Boy mower. If your model is equipped with a fuel pump, continue following the line from the fuel pump to the carburetor. If you can see two screws next to each other on the outside of the carburetor, the screw closer to the engine block is the idle air mixture screw. Use a flat head screwdriver to slowly turn the idle air screw and the main air screw clockwise until they are "seated" in the carburetor. Then turn both screws counter-clockwise one and one-half turns. Turn the engine idle screw slowly clockwise until the engine begins to sound as if it is going to stall.


Keep hands and feet away from the trimmer head while making adjustments.

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