Replacing the O-ring conversion nipples

[fourthgear]

I am replacing the O-ring conversion nipples in my 52 heads , what should I use to seal them in the heads? Any ideas on what the gap should be between the nipples and manifold? I know I should know this but, what years do these conversions work on? I see some say from 40 to 54 , are all of the manifold systems the same for these years or do Panheads differ from Knucks?

[Cotten]

Fourthgear!

Beware that a great many heads have been damaged by awkward installation of "conversion" nipples.

Most were savaged when the original damaged nipples were carelessly unscrewed, tearing out the head's threads.
Second time out is usually worse.

If your machine is anything close to restoreable, then you are adding insult to injury if you do not return to stock configuration. "Plumber's" manifolds are no longer the nightmare they were, since modern thermoplastic has solved the problems of unforgiving brass ferrules.
Either way, tips on sealing and testing are discussed at http://virtualindian.org/11techleaktest.html" onclick="window.open(this.href);return false;

You are at the mercy of your own patience and attention to detail, as nipple replacement is probably the most tedious and risky operation of all vintage motorcycle restoration. (Knucks differ in that they are MORE difficult!).
Be prepared to lathe-trim each nipple for a custom fit, and expect to try to achieve a perfect seal more than once.

Good luck,


...Cotten
(P.S.: Obviously, I am not accepting any such gigs right now!)

[fourthgear]

cotten
Well , there were no rivets in the nipple adapters and the rear head threads were gone and it was JB welded in or something. I am not worried about the authenticity of this one cause it is parts from different years and I'm not going to sell it . I will be having nipples welded in and that will solve any further leaking from an adapter and yes they are 52 heads and I would of liked to keep them org. but , she will be ridden daily and its just one less thing to have problems with down the line, I know some with plumber type manifolds will differ from my opinion but I feel I'm just bringing them up to modern standards . my two cents about it. Thanks for the reply.

[Cotten]

Since modern fuels now even affect Buna-N, o-rings are obsolete!