Leaky Fuel petcocks

[Duda]

I have a 36 VL and I have Colony petcocks on it. The damn things leak thru the petcock body. I use PLS to seal the threads into the tank and to the fuel line. I lapped the petcock to itself and it still seems to weep fuel thru the body. I used 320 and then finished with 600 lapping compound. Does anyone have any suggestion on how to keep a petcock from leaking? Lonny from Antique Cycle supply is making the earlier petcock and I have them on my 17 and they weep but not as much. Thanks

[RPjr]

Petcock

The petcocks on mine seeped (dripped), I used rubbing compound and polishing compound, take them apart and use a reversible drill and turn the center back and forth, mine are so tight now that if I do not use them for awhile they are difficult to operate and they do not leak.

[Steve Slocombe]

Colony have stopped making petcocks and so have I. The problem is the US gasoline has so many oxygenates in it that it absorbs water and rusts the metal plug in the gas tap. This is then turned into the brass body, causing scratches and hence leaks. I'm told V-Twin have made some new ones but I haven't tested them. Next time I'll make less original brass on brass petcocks, but it's not a high priority and I don't like parts coming back after sale. I have a few new but leaking petcocks I'll knock out cheaply on eBay to those of you who think they can fix them.

[RPjr]

Duda and Steve, try the drill and rubbing and polishing compound, did it 10 plus years ago and they are just now starting to weep. I have the same steel and brass petcocks. It will take a few minutes ( 5 or 10) but it is worth it. Steve saw you at the Harley Museum (36VH)

[Steve Slocombe]

Dear RP, thanks for the tip and I'll give it a try (again). That Harley museum was good, but I suspect a group of hardened AMCA judges was not the target audience. Why were there no spacer plates under the cylinders of that 36VH?

[RPjr]

Steve, mine or theirs? Mine does.

[Steve Slocombe]

Theirs. No stroker plates means it's a 74 not an 80 cubic inch bike. Or seriously pop-up pistons?? How many judging points to deduct for incorrect flywheel assembly? As I said, we were the wrong audience for a show meant to inspire the general public to own a Harley.

[Bill D.]

Leaky fuel valves

I have had troubles with my fuel valves on my wla and '57 panhead. I tried many of the recommendations - making a lapping tool, using brasso etc. I was not successful. Leakage went to a few drops but still leaked. I have two methods which have been successful:
1. I reverse engineered a fuel valve using bar stock and brass seats and polishing the existing rod.
2. Using an oem leaky valve, I drilled out the brass seat and guide. Used teflon for the seat and made a new guide bushing out of brass for the rod. I simply polished the rod which was scored pretty bad. This valve has sealed without leakage over the past 6 months. Teflon has been, up to this point, resistant to any fuel and has not reacted with any fuel that I have come incontact with.
Also, based on my experiences, I have found oem valves which were not turned true. This can be quite problematic from a repair standpoint.

[Murdog1968]

leaking petcocks

I have repaired many of these early petcocks successfully by machining a groove in the middle of the tapered portion,then using high temp o-ring(brown in color) as a seal. I have never had one of these petcocks leak after doing this repair. The high temp o-rings I used came from a friend of mine that was a diesel mechanic.

[knuckleheadtim]

I did the same thing on my in-tank as Bill D., only I used Durom intead of Teflon. Durom is very tough and easy to machine, but won't take the heat of Teflon.

I started with a brand new repro valve that was so poorly made I could have run down the road with it off. The cross-holes in the bottom of the valve were drilled after the seat was installed, and they cut slightly into the seat causing major leakage. Also. there was excessive clearance between the rod and bushing, so you could run out of fuel without being on reserve.

There is no excuse for this shoddy and dangerous workmanship. This valve wasnt cheap. Watch out for them being resold online and at swap meets. They're nice if you can repair them; useless otherwise.

[Neil74]

I lapped the valve in my Indian an used bees wax as a lubricant when assembling, didn't stop completely but much better. Would you have to cut two grooves an run one o-ring on each side of hole?

[Duda]

Leaky petcocks

I have lapped a few petcocks recently after reading all the feedback. I start with a 320 and finish with a 600 lapping compound and do it by hand. I find it works better by hand and does not take that much time. when I re-assemble I make thicker washers to pull everything together tighter. Seems to work but it has only been a few weeks.

[montij]

Suffering this same issue many years later.

1931 VL came to me with slight petcock “sweat” and one petcock with a stripped thread gas line side, so I decided to “replace” them both with new ones from Vtwin. So terribly disappointed.
The Vtwin ones leak badly from the body in the off position. I’m looking to have the originals repaired now somehow.
The Vtwin website even says:
“*NOTE: Dissemble petcock, remove cotter pin, and use
fine compound to "lap in" taper for a non-leak seal.”

shouldn’t this be the manufacturers job!?

I want to follow in the previous posters footsteps but I only have valve grinding compound. I fear it may be too coarse.

[dukekleman]

As Merdog1968 mentioned, I also use Viton Flouro. Brown O-rings in petcock valves to stop fuel leakage. I've Been using them well over 25 years now and they work great. However ,They do need replacement overtime like any O-ring, Gasketing material or seal.
Duke

[tomfiii]

O rings stop valve from dripping ,but gas will still not completely shut off. A little EZ-Turn on valve before assembly helps.