Throttle Valve Lift

Throttle valve is slightly lifted during coasting by vacuum governor on carburetor. Vacuum governor is controlled by oil temperature switch, switch-over valve and RPM switch. When oil temperature is above 77°F and engine speed over 2000 RPM, switch-over valve will be activated and will vent vacuum governor, thus governor's spring will lift throttle valve. With oil temperature below 77°F (temperature switch closed) or engine speed under 1800 RPM (RPM switch open), switch-over valve will be deactivated and vacuum will be restored to vacuum governor. This will allow throttle valve to return to idle position.