Leaky Fuel petcock shut off valve

[NiteOwl]

I have searched the forum and found handfuls of information, however I am still at a loss and nowhere did I find some pictures to help me understand what I can do to seal my shut-off valve.

I have attached a couple photos of my problem valve. I soaked it in cleaner and removed all the rust etc and cleaned up the threads.

Problem I first see is that there is a large clearance between the valve shaft and the bushing inside the valve body itself.

Next problem is that I can't get a clean turn back and forth to do any lapping of my valve face and seat because when i turn in the spindle it of course seats hard against the valve. (I am use to lapping valves that spin freely).

I would welcome any suggestions on what might work to get a decent seal. I have read about RTV solutions and cutting o-ring grooves (I like this one). The slop in the spindle has me really worried as obviously I don't really have a reserve. I am certainly open to obtaining a new setup as this one appears to be an aftermarket configuration? or not?

IMG-20120206-00040.jpgIMG-20120206-00041.jpgIMG-20120206-00042.jpgIMG-20120206-00043.jpgCentral Saanich-20120203-00038.jpg

[c.o.]

Hey Bob,

Is it leaking fuel to the carb when shut-off or just plain leaking?

Have you checked to make sure the top and bottom holes in the tank are in line?

Is there paint on the underside of the tank where the brass seal sits? If there is, it may leak.

I think that it's the seal that holds the rod up for reserve. Have you had a good look at it? Does the seal area on the rod show any signs of wear? If it's worn it won't hold the seal up. Is there a chance that the rod is bent? You can straighten it if it is but be super careful. The valve seat can be repaired but it does look like you have a reproduction so I guess it's up to you as to whether you want to repair it or just replace it.

When one of the "gurus" has a look at your thread, I'm sure a clear solution will appear. If not, I'll hit the books and get you some solid info.

[BigLakeBob]

My suggestion, take the rod you have a redress the taper either on a lathe or grinder getting the best finish you can. Get a second rod and do the exact same, then machine the threads off the second rod then use this one as a lapping tool(or just take another piece of steel and make a lap simulating the rod configuration-cast iron would be better if available). If it wears while reseating just redress it again and lap some more. Bob

[NiteOwl]

Hey Bob,

Is it leaking fuel to the carb when shut-off or just plain leaking?
Have you checked to make sure the top and bottom holes in the tank are in line?
Is there paint on the underside of the tank where the brass seal sits? If there is, it may leak.

I think that it's the seal that holds the rod up for reserve. Have you had a good look at it? Does the seal area on the rod show any signs of wear? If it's worn it won't hold the seal up. Is there a chance that the rod is bent? You can straighten it if it is but be super careful. The valve seat can be repaired but it does look like you have a reproduction so I guess it's up to you as to whether you want to repair it or just replace it.

Hi Cory, The seal to the tank and around the bango fittings is spot-on, no problem at all, the rod is actually in great shape.

The issue I have is the seat leaks, not in gallons but it dribbles, perhaps I will have a look today for a piece of similar steel to lap in the seat as BigLakeBob suggests.

The other thing of course is the large clearance between the shaft and the bushing, there is no way I will have a reserve with that much clearance. I am considering weakening the shaft by cutting in an o-ring groove to seal the bushing and shaft, but I should not have to do that.

I wonder if there is a place to buy an original or NOS, hmm probably not after all these years and the problems people have.

[T. Cotten]

Folks,

I found it quite disappointing to go through the whole rod and seat dressing routine,
and even making a PEEK tip for the rod,
only to finally determine that fuel was leaking around the pressed-in seat.

....Cotten

[silentgreyfello]

This has been discussed before. Try this:

http://www.antiquemotorcycle.org/bbo...aking+petcocks

[Erdos]

You may also need to align your tank. It is an easy process and v-twin sells the tool.

[upsrod]

This has been discussed before. Try this:

http://www.antiquemotorcycle.org/bbo...aking+petcocks

That thread is for an earlier valve.

[NiteOwl]

I found it quite disappointing to go through the whole rod and seat dressing routine,
and even making a PEEK tip for the rod,
only to finally determine that fuel was leaking around the pressed-in seat.

Hi Cotten - I know that you have been on many of these fuel shut-off valve discussion before and I value your learned opinion. I have a newbie question: What does PEEK stand for? (is it the polishing compound).

Also, does anyone have a suggestion or a source I might approach to rectify or buy refurbished? (I have in the back of my mind the inline valve you suggested to others, and if I can't get this thing to work i will go that route.

Others have mentioned that perhaps my alignment is off, I think I am good to go for that, I have no issues with the tank seal, only the valve face (and now perhaps its also the valve seat that has a weeping problem), everything fits in smoothly and appears correct, but for now the problem remains, ie the valve face and certainly the issue with the rod and the bushing not being tight.

[BigLakeBob]

Folks,

I found it quite disappointing to go through the whole rod and seat dressing routine,
and even making a PEEK tip for the rod,
only to finally determine that fuel was leaking around the pressed-in seat.

....Cotten

Have you found a way to fix the pressed in seat or do you need a new part? Bob

[NiteOwl]

This has been discussed before. Try this: http://www.antiquemotorcycle.org/bbo...aking+petcocks

Thank you for the link, I have seen that post before. I did not understand the RTV thing as it appears to me this leaves some RTV silicone on my valve face? Would that not eventually come off and cause a real problem? When I originally read through this procedure I thought is the RTV going on the face, or on the shaft, I am sorry but I just can't get a visual. The other part of that posting thread talked about LAPPING, I still cant see how the rod being used can be lapped in, as the threads on my rod (see pic above) stops me from lapping in the traditional sense. I think that thread was referring to a different designed shut-off but I am not certain.

Thanks for all the suggestions and comments, hopefully I can get to a resolution and it might help others in the future.

[Kozy]

Nite Owl, The link takes you to a discussion on a '39 which has a differant shut off arraingment than what you're working with. "39 has petcocks on the bottom of the tanks rather than the through tank shut off, the RTV mentioned is probably applied to the tapered portion of the petcock which seats against the inside of valve body. Sometimes the through tank valve and seat can be remated with a burnishing action which is forcing the face of the stem against the seat by over tightening.

[NiteOwl]

Sometimes the through tank valve and seat can be remated with a burnishing action which is forcing the face of the stem against the seat by over tightening.

Ok, now I see, . . . I was reading so many threads and did not realise there were different styles of shut-off's. So the burnishing method I had read about was hitting the end with wooded handle and turning it in tight to (grind in a snug fit). I will try that tonight. Thanks, things are getting clearer. Any suggestions out there for the loose fit of the shaft to the bushing?

Mine is a 42.

[c.o.]

I don't know how far you want to take this Bob, but I've heard of a repair where you bore out the old seat and have a new one machined.

[T. Cotten]

NiteOwl Bob!

PEEK is a remarkable plastic call PhenylEthylEythlKetone, available from suppliers like MSC Industrial.
Folks around the world are cutting or molding it to solve many problems, especially those that involve unforgiving brass.

And lapping may be a step towards a good seal, but not the last.

And BigLakeBob!

I have a box of seats and rods on my project bench. Unfortunately, other distractions take priority, and my debacle with the burnishers has exhausted my available R&D time. Things stalled out when I realized I needed to devise a test manifold to assure the original seat leaked before I ruined it.

....Cotten