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Thread: Leaky Fuel petcock shut off valve

  1. #11
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    Quote Originally Posted by silentgreyfello View Post
    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.
    Bob Beatty
    AMCA 19209

  2. #12

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    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.

  3. #13
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    Quote Originally Posted by Kozy View Post
    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.
    Bob Beatty
    AMCA 19209

  4. #14
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    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.
    Cory Othen
    Membership#10953

  5. #15
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    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
    Last edited by T. Cotten; 02-07-2012 at 08:30 PM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  6. #16
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    I found out if you overtighten the rod the male threads are fitted to the rod on fine splines and can be forced up the rod and the rod will spin making you think the threads are stripped. I applied loctite and put the threads back in place and it's all good. Now I just drain the tanks if it's going to sit for a couple of weeks.
    I like the idea of making a rod without the threads to lapp in the seat. May try that next.
    Kerry

  7. #17
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    Jan 2002
    Location
    South Dakota
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    We are in the process of making through the tank gas shutoffs with a PEEK tip, but have to finish assembling them and then testing. They should be available by summer.
    Carl

  8. #18
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    Quote Originally Posted by c.o. View Post
    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.
    Thanks Cory, I may go down that road. I think I am getting a tight seal on my valve seat now, I will try it and see how long it lasts, I am thinking it may last awhile as its a hard valve landing on a relatively soft seat and it gets turned in to make the seal... I will see..

    The outstanding problem is the generous clearance between the spindle and the bushing. I may remove the bushing and install a new one. I hope that one maybe available so I don't have to test my machining skills after all these years. grin.

    Carl, I see that you maybe supplying the peek tips, if they are fitting my style assembly I would certainly be interested and will keep my eye peeled.

    I appreciate all the feedback and it has been very helpful.
    Bob Beatty
    AMCA 19209

  9. #19
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    Bob, if you've got machining skills, I think you'll find some satisfaction in crafting a bushing yourself if you have to.... It's just a hunch I have....
    Cory Othen
    Membership#10953

  10. #20
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    I think your right Cory. I took it to my work today and will get to it this week. grin
    Bob Beatty
    AMCA 19209

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