Carbs

[Mike Costigan]

I'm another fan of the FZB. I've now run both an FZ and an FZB on the same engine; both carbs have been rebuilt by Dave, and my first impressions were the rebuilt FZ was brilliant compared to the same carb in un-rebuilt state. But then I swapped to the FZB, and that has shown a marked improvement on economy, power and general performance. Handle with care, 'cos they are fragile, but give me the FZB any day.

[Adam Brown]

My main issue is that I don't really know what I'm doing. I'm willing to learn and understand the basic principles of a carburetor but I don't know how these work.

The car was my grandfathers and I want to get it running well again. We have plenty of other vehicles (I'm not a total novice - just an enthusiastic amateur), but the Chummy is defeating me slowly. There is also lots of help on hand locally at the Cambridge Austin Seven Club if I need it.

I can't work out how to attach photos but it all looks quite worn and gnarled. I'll throw it in the ultra sonic tank today and see if that helps. I'd rather keep the car as is and the bronze FZ was a halfway house idea. I'm more than up for sorting this one out if it can be done whether that be me doing it or sending it somewhere.

I'm just at sea with it really. We had the car out last April (cold day) and it ran beautifully, it didn't go out again till June and it was a mild day but it struggled and had to be retired. If we have confidence in it, we'll use it more and I want to see it used and enjoyed - or whats the point in having it! Both my sisters will drive it but it needs to be a bit more reliable.

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With all that said, I've just removed what I think is the slow running jet (the one that screws down from the top) and it has a split at the bottom and shows many signs of 'fettling' previosly.

I've had a rummage and found two other FZB's here one with a severely braised and buggerised jet and one that is better than what I have. I would think a swap is in order?

[Mike Costigan]

Ahah! The split in the slow running tube is a typical fault which will, indeed, upset things. they can be repaired by closing up the split(s) and adding a light solder coating to seal things. (Dave Mann will no doubt be horrified at such a bodge!)

[Howard Wright]

Hi Adam

The slow running adjusting device is often split.  I soldered the slit up on mine and it improved running no end. Willie MacKenzie sells a new adjuster, he also does the main and compensating jets.

You should get a copy of “Hints on Fitting and Adjusting Zenith Carburetter” David Cochrane sells a reproduction of this little booklet. It helped me a lot!

Cheers

Howard

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Hi Adam

Willie also sells floats, needle valves and bob weights for the float chamber.

Cheers

Howard

[Dave Mann]

    The split is caused by screwing the adjusting screw down hard onto the jet which is conical, Mike's repair was what an acceptable repair before Willie started supplying new ones. I wonder if the fuel level is correct Adam, I set this on my external work bench using an old lawn mower fuel tank. Another cause of problems is worn or bent needle valve weights.

[Adam Brown]

Well I've cleaned it all out, and fitted a new slow running jet (without split) as I had one in an old carb.

Is there a simple way of roughly setting it before fitting to the car?

[Reckless Rat]

Tank off a Suffolk Punch, Dave? I have one too, and the engine. The rest went in the scrap yonks ago. I still haven't come up with an idea as to what to use it for...

[Dave Mann]

I initially set the slow running screw at 1 turn open Adam. Yes Reckless, the fuel tank was the only item i had use for.