Always use a fresh fuel mix, and mix the fuel in the correct oil to gasoline ratio.
Adjusting the carburetor on a Weed Eater, or any two-cycle engine, is necessary from time to time. Carburetors can be finicky in engines that require an oil additive in the gasoline mixture. Fortunately, it only takes a few minutes to adjust the small carburetor on a Weed Eater.
Locate the two fuel-adjustment screws on the side of the carburetor. One will be labeled "Hi" and the other "Lo." The "Hi" screw regulates the engine at full throttle and the "Lo" regulates the fuel when the engine is idling.
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Tighten the screws with a small Phillips screwdriver to position the needle end of the screws into the "jets" of the carburetor.
Adjust the screws. Turn the "Hi" jet screw counter clockwise 1 1/2 turns. Turn the "Lo" screw 1 turn, counter clockwise. Pull out the choke and start the engine. It will sound a little rough, but try to keep the engine running by applying the gas throttle. The engine needs to be warm for a proper adjustment.
Slowly turn the "Lo" screw counter clockwise until the engine idle smooths out. The engine should run smoothly without stalling or dying, but not so fast that it turns the head of the Weed Eater.
Push the throttle to full open and observe the engine. If the engine sputters, turn the "Hi" screw clockwise less than ¼ turn until it smooths out. The exact adjustment of the "Hi" screw setting depends on the size of the load, the Weed Eater head and the fuel's freshness.
Operate the Weed Eater. Keep the small screwdriver in your pocket to make minor adjustments.