The carburettor on a Homelite weed trimmer comes with adjustable screws that allow you to increase or decrease the fuel and oxygen ratio in the carburettor. These screws are set at the factory and, while minor adjustments can be made, the screws have plastic limiter caps that prevent counterclockwise adjustment. This safety feature prevents serious internal engine damage from improper carburettor adjustment and complies with federal Environmental Protection Agency standards. Do not remove these limiter caps or you will void your warranty.
Turn on the Homelite's engine. Run the engine at a high idle for at least 10 minutes to obtain the proper operating temperature. Locate the carburettor adjusting screws, located between the air filter and the engine on the carburettor. The high and low speed screws will have plastic limiter caps on them.
Locate the low speed screw, or the screw to the left. Turn this screw clockwise, noting the effect on the engine. Turn the screw back counterclockwise, noting the effect on the engine. Locate the point in between these two settings that achieves the best running sound.
Locate the idle speed screw, just above the low and high speed screws. Turn the screw clockwise until the trimmer head starts to spin. Back off the screw slowly until the head stops spinning.
Locate the high speed screw, or the screw to the right of the low speed screw. Turn this screw counterclockwise until it cannot be turned any more. Make any adjustments to the low and idle screws as necessary after the high speed is adjusted.
Adjusting the high speed setting beyond the maximum setting will damage your engine.