I have a Series II with freshly re-built Zenith carbs. Both of these carbs have two idle screws, one on top and the other below the throttle shaft. My maintenance manual refers to one or the other but not both on the same unit. The only way I've been able to get the car to run is to screw the top ones all the way down shut. Am I missing something here or did some previous owner combine two carbs incorrectly, top from one and bottom from the other? It might help to know that I do not know the position of these screws before re-build and that the re-builder left them open. I suspect previous owner had them shut. Otherwise the carbs flooded constantly.
Bill
Which model Zeniths? WIA or WIP?
For 36 W carbys:
For WIP-3 "Air regulating screw is fitted instead of volume control screw"
"In those carburetters having -3 in the type designation, i.e. 36 WIP-3, the mixture control for idling is an air regulating screw, mounted higher up the body of the carburetter, in fact in the floatchamber cover. The screw is cone ended with a spring to ensure it stays in the position to which it was set. Turning the screw varies the amount of air admitted and controls the depression acting on the slow-running jet. The action is the reverse of the volume control screw, and turning clockwise the air regulating screw enriches the mixture by increasing depression on the jet. Turning anti-clockwise weakens the mixture..."
"Idling is adjusted by means of the throttle control screw (at the bottom). If screwed in the screw will open the throttle wider and increase the engine revolutions..."
from Zenith service bulletin SB 201
To get started I am assuming:
Top screw in all the way--back out 1 1/2 turns...
Bottom screw out all the way--back in 1 1/2 turns...
Top screw is delicate be very cautious.
Any Zenith experts out there?
Allan