Manifold nipple leak

[Martin Pettingell]

Back on the 13th July I posted a thread regarding my 47 UL which didn't seem to be running right. There was a lack of performance and the plugs were coming out different colours
The diagnosis was a manifold leak. It took me a while to build a manifold leak tester and get access to some compressed air
Sure enough when tested the rear cylinder was leaking quite badly around the manifold. When I stripped it down the rear nut was very tough to remove. The bike was fitted with an OEM brass manifold I guess from an earlier model.
In any event I decided to have peek seals fitted and sent the manifold and nut off to have the new seal fitted properly.
When I came to fit the new set up I realised the rear nipple was moving in the cylinder. I guessed when I pressure tested in that I would have a leak from the nipple. I was correct in fact it was much worse than than the original leak I had started out with. I guess I must have disturbed the nipple in trying to get the manifold off originally.
Having taken the carb. off and put on an old nut I can move the nipple in the threads without applying any real force. Looking inside I can see the bottom of the locating pin just rocking as the nipple moves
The nipple is going to have to be replaced for sure
Sorry that's a long lead up to the questions
Where can I get new nipple? Are aftermarket ones any good or should I try to find a NoS one from somewhere?
As the nipple is already moving in the cylinder my feeling is that it may just unscrew once the pin has been ground off but I have read that that may damage the threads in the cylinder and it is better to carefully cut through it and crush it inwards. Any advice on the best way to go would be helpful
Finally as and when I get the new nipple do I need to use some kind of sealant to make sure the threads seal air out - if so any suggestions on what is best to use?
Grateful for any pointers on getting the old girl up and running sweetly again
Thanks
Martin - from the UK

[T. Cotten]

Martin!

Contrary to popular notions, the 'fossil record' says brass is correct for late '46-47, and for Gs and OHV manifolds as well.

When the nipple has been badly over-torqued to where it is loose, it nearly always has upset the internal threads, like my attachment.
I preferred a diamond burr on a hand grinder cut and crush the nipple for removal, as described at http://www.virtualindian.org/11techleaktest.html.
Since then, most folks have preferred JBWeld for a sealer, whereas S&S uses Permatex's "The Right Stuff". Both survived my P4gas immersion tests fine, although the JBWeld is best when cured a couple of weeks. The Seal-Lock mentioned in the discussion is admirable, but not for large voids.

The major complaint with Colony reproductions was too great of a champher upon the inside diameter. They may have corrected it by now.

Please note that the threads do not seal, as they are not tapered. It is the shoulder that butts up against the casting counter bore that must seal.
The rivet is the other troublesome interface, and forcing a tapered head outward seals it internally. How the factories got away with a flat head on a curved nipple is beyond me.

....Cotten

[Martin Pettingell]

Cotton
Thanks for the helpful information
I guess I will need to get the nipple out and see what I'm left with
Martin

[BigLakeBob]

[Martin Pettingell]

Bob,

Thanks - I was looking at the JP weld - I had heard of it but never had need to use it before. Looking at the UK distributor there were lots of their products that might have worked regarding heat resistance but the period of setting seemed variable and all of them seemed to leave you with a solid joint that would not come apart again without potentially damaging the cylinder. Maybe that's what is intended but if you don't get an air tight seal first time there didn't seem much margin for error. I guess the advantage it that once its set I wont get disturbed if you need to get the manifold on and off in the future
Is there a particular jb weld product that has used and found to work well for this particular problem?
Having looked up the gasoiler in your photo this looks like it may solve that problem - I just need to find a source for it in the UK
Also those nipples look pretty sharp. I am guessing they are repro's from somebody. Who makes 'em?

Thanks for the time and help

Martin

Thanks

[T. Cotten]

Martin!

JBWeld is a common off-the-shelf epoxy here in the USA, and I am told there are now even better "marine" grades of it.
Probably Devcon and other epoxies are equally durable, but I haven't tested my local fuel with them.

The original red Gasoila failed miserably in my immersion tests (as did Glyptal; Those who sealed the insides of their motorcases with either should take every precaution to prevent fuel from contaminating their oil.) I haven't tried others, nor have I tested in a couple of years.
Please remember its about the variety of fuels and dozens of other additives than ethanol, not the sealer itself.

From feedback I have received, fuels just about anywhere else are less corrosive and digestive than in the USA.

....Cotten

[BigLakeBob]

Bob,


Having looked up the gasoiler in your photo this looks like it may solve that problem - I just need to find a source for it in the UK
Also those nipples look pretty sharp. I am guessing they are repro's from somebody. Who makes 'em?

Thanks for the time and help

Martin

Thanks

The one on the left is Colony, the one on the right I made. I oversized tapped a stripped out pan head to 1 13/16 -18 and made this nipple to fit.