Zenith side draught carb mixture adjustment 12/4

[Charlie54]

I wondered if anyone has any advice on adujusting the Zenith carb I have on my 12/4 Clifton. On start up idling it repeatedley wets no 3 & 4 plugs.

Running the engine at increased revs results in the plugs firing ok as indicated by shorting out each in turn and hearing engine tone fall. But on idle the plugs get too wet. The spark is good from a coil igntion , the timing is right on the mark with my strobe at idle. Ive checked compression and no2 is a little low at 72psi but 3&4 are good at 82 and 90 psi.. The spark is big and healthy. Im suspecting the the slow running adjusting device on the carb.

Ive cleaned it but did notice that the male and female conical jet & seat dont look convincingly as described in the Zenith hand book. I would say the female tube (G) is not a taper seat for the male jet (A) . I could hazard a guess that through its life it may have been heavy handedly rammed together so as to distort the female seat. I dont seem to be able to tune the carb to a nice steady idle and think it may be running very rich and wetting the plugs , but why just 2 i dont know.
Anyway my question is, has anyone ever tried lapping the male and female parts together to give a good fit when fully screwed in to the richest position? I may be barking up the wrong tree with this as seperating the seat and cone should weaken the mixture at idle , so a little distortion would be an irrelevence.
Any advice appreciated .

[Fuzz Townshend]

Apologies for this late response…
A little while ago, Tony Smallbone suggested to me that replacing the slow running jet often transforms engine characteristics on Austin 12s.
I duly purchased a new jet and overhauled my car’s carburettor, and hey-presto, he was right.
I’d suggest getting in touch with Tony.

[Charlie54]

Thanks Fuzz . I think i'll try a new jet if i can find a source. I did check the Burlen website and couldnt find any jets listed for mine.

[panaflex]

Try Derbyshire Austins for spare carb parts. It's where I got mine.

[Charlie54]

ill give it a try thanks

[Charlie54]

New slow running jet assembly (cone and taper) fitted, its made a world of difference to the idling .

Thanks