1974-76 Models
- Check for loose, disconnected or deteriorated vacuum hoses. Replace as necessary. With engine idling at normal operating temperature, disconnect vacuum hose from intake manifold and connect hose directly to throttle opener diaphragm. See Fig 1.
- Observe that throttle opener rod retracts when engine speed is increased. Reference mark on throttle opener bracket should be between adjustment marks on throttle lever.
- Check throttle opener rod for full retraction of 0.20" (5 mm). If fully retracted, adjust throttle opener stop screw to center reference mark between adjustment marks.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
- If full retraction is not possible, connect vacuum gauge to manifold vacuum hose. If no vacuum is present, clean port in intake manifold and check carburetor linkage for sticking or binding.
- Reconnect hoses to original locations and check that control valve will retract throttle opener at least 1/2 its total travel for 1 second when throttle is closed suddenly from 3500 RPM.
- If not, disconnect hose connected to 4-way fitting and air temperature control check valve. Connect a vacuum gauge to hose. When throttle is closed suddenly from 3500 RPM, vacuum reading should be 19-20 in. Hg. If not, turn control valve adjustment screw.
Courtesy of AMERICAN HONDA MOTOR CO., INC.