The carburetor on the two-cycle, gas-powered Troy-Bilt weed eater is adjustable. This allows you to increase or reduce the engine's idle speed. Adjusting the carburetor will allow the right amount of fuel and air to mix in the carburetor, so tuning it properly will increase the performance of your engine.
You should never turn the idle speed up to the point that the trimmer head rotates while idling. If you re-tune your carburetor improperly, you can damage it.
Before Adjusting the Carburetor
Remove any old or bad gas. Pour it into an approved fuel container. Fill the weed eater's tank with freshly mixed, two-cycle engine oil.
Unscrew the air filter cover with the large flathead screwdriver. Pull the air filter from the mounting box. Wash it in the soapy water. Allow it to dry before using it again and adjusting the carburetor.
Unscrew the muffler cover with the large flathead screwdriver. Unscrew the spark-arrestor screen. Clean the screen with the brush and soapy water and then use the brush to scrub the muffler's exhaust port clean.
Replace the spark-arrestor screen. Set the air filter into the engine. Screw the air filter and muffler cover into place.
Adjust the Carburetor
Pull the starter handle to start the engine. Let the engine idle for several minutes to heat it up.
Insert the small flathead screwdriver into the hole on the air filter cover. You can locate this hole--about the size of pen tip--on the top right of the cover.
Turn the screwdriver clockwise 1/8 of a turn to increase the idle speed. Continue using 1/8 turns until the engine idles smoothly in your hands. The trimmer shouldn't "die" when idling.
Turn the screwdriver counterclockwise 1/8 of a turn to stop the head from spinning.