CHOKE COVER TENSION
The Zenith carburetor is equipped with an automatic choke which is controlled by an electrically heated bi-metal spring. A connecting rod keeps the choke under the tension of the spring which responds to any change in temperature. When the engine is cold, the spring holds the choke closed. When the engine starts, the gap control unit opens the choke to prevent over enrichment.
TROUBLESHOOTING
If the choke cover tension is not properly adjusted the following could occur
- Warm up problems
- Stumbling, stalling, hesitation
ADJUSTMENT
- From the factory, both choke covers are adjusted 5mm in the rich direction
- Re-adjustment is required at the second vehicle service
CHOKE TIE ROD
FUNCTION
The function of the choke tie rod is to tie together the operation of the choke plate, bi-metal spring, high idle cam and choke gap
NOTE: Prior to making any adjustments related to the choke, the tie rod must be adjusted to its proper basic length. This insures that when the choke flap shuts, the high idle cam is turned fully to the high step
ADJUSTMENT
- Block throttle linkage partially open to free choke cam
- Loosen set screw at top of choke rod
- Lift relay lever at bottom of choke rod to its full up position
- Close choke flap fully, allowing connecting lever to center itself, and tighten set screw
NOTE: Late types have 1.5mm allen set screw
CHOKE FAST IDLE SPEED
FUNCTION
The fast idle speed is critical in keeping the engine running at sufficient speed to overcome the increased resistance of the engine when cold
TROUBLESHOOTING
If the choke fast idle speed is not correct, the result will be insufficient chokespeed (stalling) in a cold engine, or excessive speed causing rough engagement of the transmission.
NOTE: Before proceeding with adjustment, remove and discard fast idle speed adjusting screw and screw tensioning spring in the rear carburetor, if one in installed.
ADJUSTMENT
- If a 100*C temperature switch is installed in thermostat housing, ground cable end so necessary advanced ignition timing is provided
- Crack open throttle
- Close choke flap by lifting choke relay lever. Release throttle
- Start engine without touching throttle. Observe RPM
- Adjust to specified RPM at front carburetor fast idle adjusting screw
CHOKE GAPS
FUNCTION
The choke gap control opens the choke flap slightly to allow the engine to breath after starting
TROUBLESHOOTING
Choke flap or linkage binds: (Flap won't close or binds and won't open) Causes rough idle running and possible stalling when engine is cold
ADJUSTMENTS
- Set carburetor at fast idle by actuating choke step cam. To do this, crack open the throttle
- Close the choke flap by lifting choke relay lever
- Release throttle
- Start engine without touching throttle
- Lift relay lever at bottom of choke rod to its full up position
- Using a rod of proper diameter, measure the gap present between the lower flap of the choke and the carburetor housing
- Adjust at the adjusting screw on diaphragm housing
