Servo Diaphragm

Start engine, set engine to 700-750 RPM. Stop engine and disconnect vacuum sensing tube between vacuum control valve and intake manifold. Connect tube to intake manifold and servo diaphragm, attach tachometer, remove vacuum sensing tube between carburetor and distributor. Start engine and check engine RPM. If engine RPM is 1400 ± 100 RPM (1800 & 616), 1300 ±100 RPM (1200) or 1200 ± 100 RPM (808) servo diaphragm is normal. Achieve specified RPM by adjusting throttle opener adjusting screw. Disconnect tube from intake manifold, engine speed should return to 700-750 RPM. If preceding checks can not be achieved servo diaphragm is defective.