Weed Wacker Wont Idle . To adjust the l screw, start the weed trimmer and turn the screw counter clockwise until the speed of the engine decreases. Check the fuel quality and pour fresh gasoline if required. Weed Eater Carburetor For Ryobi Homelite 25cc C1UH60 Fuel Line Primer from www.ebay.com Make sure the fuel line doesn’t slip from your hand. If cleaning the carbon fixes it, all is well. To adjust the l screw, start the weed trimmer and turn the screw counter clockwise until the speed of the engine decreases.