We should have made ourselves clearer. The car is unwilling to idle. On the road, it is very prone to stalling when stationary. A touch on the throttle to keep it alive, sends the revs too high and lifting off stalls it. With the car in the garage, there are two adjustments; the idle mixture screw and the idling speed screw which alters the stop point of the linkage. The idle mixture screw does not make much difference to the problem as the engine behaves about the same with the screw three turns out or one turn out. Rich mixture at idle often causes hunting but in this case it would seem not to be the culprit. The only way to keep the engine from stalling is to idle it too fast when it hunts like an old fashioned diesel in a trafic jam. Adjusting the idle speed screw does not gradually slow the idle down; it goes from revving too fast to stopping completely with nothing in between. We have a spare carb and the idling jet in both is a 65 suggesting that is correct. Are the jets common to other Zeniths? What are we looking for if we wish to change jet sizes?
It occurs to me that the butterfly spindles may be worn enough to let in air. Is that a possible cause of poor idling? If it were a SU, I would know my way around it and would also know who to send it to for rebushing the spindles. What we are really asking is if anyone has had similar symptoms with a similar carburetter and has fixed the problem. At the moment, there are three other pre-war cars here which tick over like gas engines but they use Amals and SUs which are simple, trouble free and well brought up. We have a reasonable amount of literature on the 36VI 2, but none of it is helping. The Zenith is taking the gilt off our gingerbread.
