To adjust the carburetor of a weed eater, the owner must look for the two fuel adjustment screws that are located on the body of the carburetor. These two screws are usually marked as HI and LO. The HI screw allows for fuel adjustment at full throttle, while the LO screw allows for fuel adjustment during engine idle.
When you are first adjusting the carburetor screws, tighten them clockwise until they first start having resistance. This is considered the reference position. To start, the HI screw should be screwed 1.5 turns counter-clockwise. The LO screw should only be screwed one full turn counter-clockwise. After the screws have been adjusted, fully pull out the choke.
Once the choke is open, the owner can start the weed eater. The engine fails to idle by itself at this point, and enough throttle must be used to keep the engine running. With the engine still running, adjust the LO screw one-quarter of a turn at a time until the engine idles smoothly without help. For the HI screw, the owner should apply throttle to see if the engine sputters. If it does, this means it's receiving too much fuel, and the HI screw needs to be adjusted in one-quarter turns clockwise. After each turn, apply throttle to check if the engine is running smoothly.