1976 Models
- Connect tachometer to engine. Start engine and allow to reach normal operating temperature (cooling fan comes on). Disconnect hose from throttle opener diaphragm and connect a hand-held vacuum pump.
- With engine running, apply at least 16 in. Hg of vacuum for more than one minute. Check that engine speed rises to RPM shown in THROTTLE OPENER SPECIFICATIONS table.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
- If speed is too low, widen adjustment slot in throttle control linkage. See Figure. If speed is too high, narrow slot opening. If speed cannot be adjusted, or diaphragm will not hold vacuum, replace diaphragm and repeat test.
- Reconnect vacuum hose. Raise engine speed to 3500 RPM and maintain for 2-3 seconds. Quickly release throttle. Engine should return to idle in 1-4 seconds. If throttle closes in less than one second, go to next step. If throttle takes longer than 4 seconds, go to step 8).
- If throttle closes in less than one second, disconnect vacuum hose from throttle control diaphragm. See Fig 3. Connect a vacuum gauge to hose. Raise engine speed to 4000 RPM. Vacuum should be at least 1.2 in. Hg.
- If vacuum exists, by-pass throttle control valve and repeat step 4). If throttle control diaphragm is good, replace control valve. If throttle stills returns in less than 1 second, check voltage at dashpot solenoid.
- If voltage (12 volts) exists, replace dashpot solenoid. Remove throttle control by-pass and repeat step 4). If vacuum is below minimum, check hoses for leaks, or blocked carburetor port.
- If throttle takes longer than 4 seconds to return, replace by-pass throttle control valve and retest. If return time does not change, replace dashpot.
- If return time is now within limits, check throttle positioner solenoid for voltage. If voltage exist, replace speed sensor. If no voltage exists, replace throttle positioner solenoid and repeat step 4).