Idle Mixture
NOTE:
Mixture adjustment is NOT a part of normal tune-up procedure and should not be performed unless mixture control unit is replaced or vehicle fails emissions testing.
- Warm engine to normal operating temperature. Remove rubber seal from duty cycle test connector. Connect positive lead of dwell meter to Blue/Red wire, and negative terminal to Black/Green wire. See Fig 1 .
- Start and run engine at 1500-2000 RPM for 30 seconds and allow it to return to idle. Duty cycle should be 10-50 degrees at 750-850 RPM. If not, remove carburetor from engine.
- Drive out idle mixture adjusting screw retaining pin with a .18" (4.5 mm) rod to gain access to mixture adjusting screw. See Fig 2 . Install carburetor.
- Start and run engine at 1500-2000 RPM for 30 seconds and allow it to return to idle. Duty cycle should be 10-50 degrees at 750-850 RPM. If too low, back out idle mixture screw. If too high, turn idle mixture screw in.
- If adjustment is correct, check idle speed and adjust if necessary. Install rubber seal in test connector and drive in idle mixture adjusting screw pin. If duty cycle cannot be adjusted, check carburetor feedback system.