Zenith carb question

S2a, 2.25 petrol, Zenith carb, 70k miles.

Running well, but running rich. Started after 5 secs with or without choke, small amount of black smoke while running, doing about 15mpg. All the indications are that it's running rich. Adjusted volume control screw as per manual to no effect, so I decided the carb needed an overhaul. Got an overhaul kit and did the work over the weekend.

Now it starts first turn and idles sweetly - even first thing with no choke. Misfires a bit when it's revved, loads of black smoke. Obviously running very rich. Adjusting the volume control screw makes no difference whatsoever to the idle speed, from fully closed to right out (at which point it stalls, not surprisingly. VCS is extremely stiff and almost impossible to turn (as was the old one). Substituting the old one makes no difference.

All I did to the carb was to replace the jets and economy device diaphragm and set the float level to the correct setting (33mm from the gasket face - it was 28mm which is 5mm out - but this would weaken the mixture, wouldn't it?). Obviously I've done summat wrong, but what?

Anyone any ideas? Or should I junk it and get a Weber?

TIA

Rich

Series 2a The rest

Reply to
Richard Brookman
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On or around 25 Oct 2004 01:00:45 -0700, snipped-for-privacy@yahoo.co.uk (Richard Brookman) enlightened us thusly:

sounds like you have a blockage somewhere, or a leak letting petrol in where it shouldn't. The mixture screw should have some effect. I assume you had the correct main jet to put in?

IIRC, on the zenith, the adjustment is for idle mixture only, not for normal running, which is defined by the size of the main jet and auxiliary jet if it has one. 's ages since I played with a zenith, though.

Reply to
Austin Shackles

Two main problems, and both about the sealing between top and bottom. There's the O-ring which seals around the actual air passage, and they're also prone to the casting warping. This means that the gasket doesn't seal, and lets petrol leak into a little hole, and thence into the air. I think the particular hole is one of those towards the engine-rear.

I've seen a suggested fix involving plugging the hole. There's a web page about this on a site run by one of the American Land Rover outfits, or was it actually in Canada?

Reply to
David G. Bell

So Austin Shackles was, like

It came as a kit (unlabelled) but all the jets I replaced were visually identical to the ones I took out. I just removed every jet one by one and replaced like for like. There was one jet left over that I didn't use, however, and a load of spire washers and plain washers that didn't belong at all... perhaps the kit was wrong.

You're right, although it is important to set the idle mixture correctly as the carb will draw fuel through the idle circuit at all times, affecting the mixture vthroughout the range, AIUI. At the moment, screwing in/out the volume control screw makes *no* difference. Normally, it goes from stalling (too rich) to maximum idle revs, to stalling (too weak) in about 3 turns. I'd only just set the idle mixture a week before, so I know it's not working the same.

I'll swap the main jet back for the old one and see if it helps. Grateful for my policy of "throw nothing away until you're sure the new stuff works".

Cheers

Reply to
Richard Brookman

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