Fuel leak from carb

[David Stepney]

The one sealant that is petrol resistant is good old Red Hylomar.

[Ian Wegg]

Thanks, Graham and everyone for the help. I will keep a lookout for a replacement carb (there are a couple on eBay) and will try some of the suggestions in the meantime.

[Reckless Rat]

The weakest part of the Zenith 26VA is the fuel banjo thread. Don't buy another one unless you've tested the quality of the thread with a good banjo bolt.... caveat emptor.

[Ian Wegg]

Just a quick update on my incontinence problem!

I discovered that the reason I couldn't tighten the banjo bolt wasn't that the thread in the Zenith carb was stripped, but that the new bolt I had bought was slightly too small.



The new one (left) is 12mm in diameter whilst the one I had removed (right) is 12.5mm. I got the replacement banjo bolt from one of the club's recommended suppliers so I'm sure it is correct. My conclusion is that the Zenith carb standard connection is 12mm (M12?) and my carb has been drilled and retapped 0.5mm larger (possibly 1/2" UNF?)

I could put back the old bolt but would really like a new one if anyone knows where the 1/2" bolt comes from. Also, a filter for it would be nice as, of course, the standard one is too small.

(I have now ruled out getting a replacement carb as prices seem to be eye-watering)

[Graham Barker]

Hi Ian,
Life's not simple, is it?  Especially with cars that are over 80 years old.
Regards
Graham

[Bob Culver]

AS previous posting where I absent mindedly  referred to original as 7/16 it is actually 12mm and often readily taps tp 1/2 UNF almost the same pitch over a short length and the size used in later Zeniths. I have recovered several carbs this way.

[Andy Bennett]

Am pretty sure the original thread is M12 x 1.25 as I bought a tap to clean through a grubby thread on a new carb a while back.
One of our members swears by helicoiling when stripped. Appreciating Ian's has already been enlarged, but in general it has to be worth a go if the alternative is the bin.

Andy

[David.H]

As I recall Zenith and Solex had French backgrounds, hence Metric threads. I think I put some m7 (?) helicoils into one of my carb bodies.

[Bob Culver]

Helicoils and taps for are expensive. A 1/2 UNF tap good enough for zinc commonly and cheaply available, often in 2nd hand shops. The UNF fitting is standard on a myriad post war Zeniths. If anyone in NZ can use I have many ex Javelins.

[Andy Bennett]

Hi Bob
Not expensive here. £15 ebay will buy you a set that could fix half a dozen carbs.