Operation Section Mixer Idle Screw / Power Valve Adjust (G643 Engine Only) Forklift have Unstable Idle RPM, You can adjust idle screw. Idle Screw turn to rich side (turn in screw) Forklift have Poor High Speed Performance, you can adjust power valve, power valve turn to rich side. Power valve marked “R” and “L”. “R” is rich side and “L” is lean side. L R 79