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MG MGB Technical - OK, this leaking carb is getting tiring...

So just finished my fourth attempt at trying to get the jet tube to stop leaking at the float bowl. Got some new seals today and tried that. Still leaks.
I was told to put the little washer on the end of the tube to keep the threaded nut on the end of the tube. And to carefully insert the grommet so that it is square in the hole, then thread the nut in carefully. Did that and it leaks. So what's next?
Ron

So according to the instructions on page 20 of http://www.bmcno.org/manuals/Tuning%20SU%20Carburetters.pdf

You're supposed to fit the brass nut then the washer, then the rubber gland onto the tube but have a minimum of 4mm of the tube protruding out, then thread it in just until the washer is compressed. Does that sound correct?
Ron

Ron,

That sounds about right. This is a compression fitting. So, the washer is there to evenly smash the rubber washer tight on the tube and tight in the bore. The nut is there to give the force for the smashing. But, if the tube is not sticking out past the washer, there is nothing for the rubber washer to smash against. Because of the spring on the outside of the tube, it can be a bit of a trick to get everything to stay in place while the nut is tightened. You need to get everything slid up on the tube, push it into the bore in the float bowl, and then keep pushing the tube into the bowl while you tighten the nut. If the tube slips out while you tighten it, it will leak. You might also check that there is no junk in the bore from the old parts.

Charley
C R Huff

I have run across some jets that have a thin brass sleeve installed in the end of the hose. I assume the purpose is to prevent the hose from colapsing when the nut is tightened. It may have varied from year to year or supplier to supplier or based on the hose material. If you can find one it may be worth a try.
John H

Also, if you do everything right, and it still leaks, you might want to examine the threaded hole where the jet assembly mounts to the float bowl a bit more carefully. If some PO also had this problem, they may have over tightened the gland nut on the jet assembly and cracked the float bowl casting. Years ago a friend found this to be the case where his float valve screwed into the cover and we had to replace the cover.

The OE SUs were not always cast well and the metal from which they were made was relatively soft, making it easy for a hamfisted mechanic or DPO to cause cracks like this in these castings. Hopefully, this is not your problem.
Bob Muenchausen

Thanks all. I used the instructions from that SU manual pdf file and it worked! I can't believe none of my other manuals explained how to assemble it. This jet tube does have the little brass fitting on the end. Anyway, so far no leaks so I can continue on with preps for the big brit car show next weekend. :)
and now my B has the "proper" carb port vacuum advance setup with a eurospec 45D4.
Ron

This thread was discussed between 07/05/2008 and 08/05/2008

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