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Original Post (Thread Starter)
#813471 06/21/2020 10:15 PM
by Tracey Spear
Tracey Spear
Well I took the original push/pull petcocks apart on this '69 Thunderbolt I'm rebuilding. It took me a minute to realize I was looking at 50 year old cork.

Seems I can purchase upgraded plungers with O rings. But those are a little pricy.

Replacement petcocks from UK are quite pricy.

Then I see inexpensive Emgo petcocks.

What's the best route to leak free fuel delivery?

Liked Replies
#813532 Jun 22nd a 07:47 AM
by Mark Z
Mark Z
Originally Posted by Tracey Spear

I was already headed in that direction. I was looking at options from the Bonneville Shop. They have a straight 1/4 turn petcock set intended for Triumph at a reasonable price. That particular petcock requires a sealing washer for BSA application.

Straight/ 90 Degree does it really matter?

On a dry-frame A65, the petcocks are so close to the rocker cover that I think you need the 90-degree fittings to allow clearance for the hose. I have the 90 degree fittings, but I run Mikunis, with an "H" arrangement in the hose, so mine is not a good example.

Yes, these petcocks have a nut that tightens against the tank, and the washers that work are the type that are rubber sandwiched inside copper.

One other issue, up to 1967 at least, A65s had larger diameter petcocks, that is, where they thread into the tank, larger than Triumph and larger than the standard aftermarket petcocks. So my bike requires adapters to bring the holes down to the standard size, which is about 1/2 inch. (Note: Petcocks are "sized" by the inner diameter, so those with a 1/2" outer diameter I believe are known as "1/4 inch".) I believe in 1968 BSA brought the holes down to the standard size, but you may want to verify this. The earlier larger petcocks are about 5/8" outer diam.

Originally Posted by gunner
I can recommend the B.A.P type of tap as sold by the Bonneville shop and other places, these were fitted to later Triumphs and Nortons and don't leak, I think these are the ones others have mentioned above. See This Link

Don't go for the other type of 1/4 turn tap with the longer flat type lever and circlip, I have several of these fail and leak due to o ring failure the threads stripping.

Gunner, my petcocks have a flat lever and a snap ring to hold the plunger in, but they have no rubber O-rings. But I think you're right that they are the type that were fitted to later Triumphs and Nortons.
1 member likes this
#814168 Jun 27th a 05:32 AM
by leon bee
leon bee
Yeah, you're supposed to drive the spindle out of the knob with a pin punch, replace cork, knob back on and peen the brass a little. Then a few years ago Norbsa, Michigan I think, mentioned just slitting the cork to install and I've been doing that ever since. Submerge new cork in real hot water for a few minutes. Trim length with a razor blade, then slit one side and carefully ease it onto the brass spindle. Have a bar of white real soap, soap up the cork and force it in there. This works just fine.

I can lean a bike way over and replace either or both sides quickly.

Don't ever let the corks dry clear out, that's when you have to boil them, etc. Over the winter my corks/spindle plungers live in a jar of gasoline.

But. You can't just buy two corks, gotta have a little bag of them. Some break and some you have to reject. And I haven't bought any for some years so don't know what parts guys may be asking these days. I've always been going to sit down and figure out how to make my own, but that hasn't happened yet.
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#813512 Jun 22nd a 02:27 AM
by Ignoramus
Originally Posted by leon bee
You just buy a bag of the corks and replace the old ones.

that is exactly what i did , but being a pedantic ex engineer i got hold of some real high grade cork (yes there are something like 5 grades of cork) and machined them down to get a good tight fit (from memory i settled on 1/2" diameter and made a little tool with a huge tapered lead in to size them to the id of the tap and boiled them before putting them in the "fixture which i froze overnight) ,,, i just soldered the spigot back on .....worked a beauty .........5 years of no leak and counting

most important is to deburr inside theof tinny little thread where the lock screw goes or it will tear the cork on insertion..........pedantic hell yeah!
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#816965 Jul 21st a 07:51 PM
by Tracey Spear
Tracey Spear
I've got the 90 Deg petcocks waiting in the wings. But respecting the elegant simplicity and correct looks of the original Ewerts I decided to attempt to refurbish the original petcocks. I've received corks and disassembled the plunger.

So.... How does one properly reassemble the petcock with any hope of proper function?

My first issue is the size of the cork. It seems a fair it large for the bore. Is this where the boiling water comes in? Does boiling allow the cork to compress into the bore?
Dry, I don't see it fittin'

Thank you
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