Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board O-ring.

Hi people. Has anyone deleted the O ring between the Tufnal spacer and carb body and replaced with gasket or loctite form a gasket or both? Cheers,Max.

Yeah absolutely! .......................................... didn't work, ended up over tightening the nuts and distorted the carb body so slider stuck wide open.......... caused a moment or two of excitement.

I find it easier to judge on how tight is two tight with an O ring.

I have used compressed asbestos fiber ( very thick) to isulate the heat on the carbs from the head on my A65 but kept the O ring as well

works fine ... i wouldnt use the magic in a tube casue its such a [***] to clean off

Hope you can find the correct O-ring, I suspect that might be the reason for the question. It the best answer.
In any case, even when I use them, I make sure I can still slightly shift the carburetor on the base to prove I have not over tightened. You can still overtighten using an O-ring, especially if it is slightly too large. It is not fail safe, and can act like a hydra static lock, with no place for the excess to escape. My

Nitrile O rings are redily avalable at any decent beraring supplier

I’ve learned the hard way any soft oring (especially a thick one) or thick gasket or plastic spacer between a Concentric and the manifold can allow the flange of the carb to be bent if you over tighten it without paying attention to the effect on the carb. Once bent it requires either straightening it yourself using a jig or sending off to someone who will straighten and sleeve it. Especially if you use an o ring make sure you don’t tighten beyond where the flange is still straight—easy to see if you watch for it.

Seems to me that a great invention would be a thin spacer plate under the carb, with a bonded "O" ring around the intake hole, rather like a Dowty washer. Then the nuts could be tightened down on the spacer with the correct pressure on the "O" ring being governed by the thickness of the rubber.

An easier way would be to calculate (or measure) the correct carb to inlet stub gap when the "O" ring is sealing correctly, and put a washer of that thickness on the carb. mounting studs before fitting the carb. Do the nuts up snug and the "O" ring seals but the flange is not stressed.

I think that works for the Triumph where the thick oring was used, but Beezers used the standard oring, so anything under there will be too much.

Toss the O ring fit a soft gasket between the carb flange & the tufnol spacer and forget about warping
From memory that is what Enfield did