1977-79 Models
- Check for loose, disconnected or deteriorated vacuum hoses. Replace as necessary. With engine at normal operating temperature and idle speed set to specifications, disconnect vacuum hose from throttle opener diaphragm and connect a hand-held vacuum pump to diaphragm.
- Draw at least 16 in. Hg of vacuum with pump and check idle speed. Engine speed should increase to 1100-1700 RPM. If engine speed does not increase, adjust throttle link lever. See Figure. If speed cannot be adjusted or diaphragm will not hold vacuum, replace throttle opener diaphragm unit.
- Reconnect vacuum line to throttle opener diaphragm. Hold engine speed at 3500 RPM, release throttle, and note time required for throttle to close. Time should be 2-8 seconds. If not, turn control valve adjusting nut clockwise to decrease time or counterclockwise to increase time. See Fig 1. If time cannot be adjusted, replace control valve and repeat testing procedure.
Courtesy of AMERICAN HONDA MOTOR CO., INC.