Checking Throttle Valve Lift
Connect tachometer, start engine and increase speed to about 2500 RPM. Release accelerator linkage and observe vacuum governor on carburetor. Adjustment screw should contact linkage lever at speeds above 2000 RPM. With a drop in engine speed below 1800 RPM, vacuum governor diaphragm will be activated, thus moving adjustment screw away from linkage lever. If test fails, check vacuum line connections, RPM switch and throttle valve lift switch-over valve.
CAUTION:
Loosen diaphragm shaft nut prior to setting adjusting screw; hold wrench on machined flats and loosen diaphragm shaft nut.