EL 1937 Petcock

[ulfhd]

Hi,on my 37 Knuckle are new Petcocks from V-Twin Looks nice, but Leaking,i hadit is there anybody out there how to Fixit ???? its imposible to Ride with the Stuff i uesed new Petcock style works grat looks ****,i need HELP thanks ULF

[Steve Little]

Hi.
We had a good discussion about sealing original taps a few years ago. I can't remember the heading of the thread but somebody else might.
I have original taps on my 37 and I spent a couple of hours checking, lapping, setting spring pressures, adding shims and bench testing mine to get a nice seal.
The tapered dowel design taps, will only seal if the peg is a perfect (unmarked) fit in the body. It will also need sufficient spring pressure to draw the metal peg into the tapered hole of the brass body.

The procedure I used to fix mine:
Coat tapered peg with fine lapping paste and lightly twist back and forth into the body . Pull it out, rotate peg 1/4 turn and repeat action a few times.
Clean all parts and blow dry.
The reason for a (light) lap, is to give the surface of both components a satin finish.
If the contacting surface of either part is still shiny from original use, or pitted, it is not contacting (sealing).
It's important to choose the correct lapping paste. If you rub some between thumb and forefinger, you should not feel the grit in the paste. It should just feel oily.

Once you have a Full contact surface on the peg and body, the next procedure, is setting the peg with enough spring pressure to draw it into the tapered hole.
Both my springs were effected by age, and heat. I still used them, but packed them with extra washers until I had the desired spring pressure.

I bench tested mine with light compressed air, and soapy water, and then fitted them back to my tanks. 4500 miles later.... no drips.

If the V Twin taps are the same design as original, they might just be suffering from (lack of finish).