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Thread: M88 Float Needle Valve Seating

  1. #1

    Question M88 Float Needle Valve Seating

    How well can I expect a stainless float needle to seal? Is it unrealistic to expect it to seal indefinitely? After several sessions with a new needle, seat, toothpaste and Flitz I got it to prevent overflowing for several hours, but it couldn't do it overnight. I always shut the tank valve off so it doesn't need to be perfect, but I'd like to know how to achieve this if possible.

  2. #2
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    Quote Originally Posted by Rex37W View Post
    How well can I expect a stainless float needle to seal? Is it unrealistic to expect it to seal indefinitely? After several sessions with a new needle, seat, toothpaste and Flitz I got it to prevent overflowing for several hours, but it couldn't do it overnight. I always shut the tank valve off so it doesn't need to be perfect, but I'd like to know how to achieve this if possible.
    The trick, Rex,..

    Is to place the seat upon a firm benchtop, place the needle within, and then smack it with a wooden screwdriver handle.

    "Suck test" it, and then hit it a few more times if you must.

    If it still fails, then you might consider a fresh repop; I prefer COLONY's, but ya still gotta whack them too.

    ...Cotten
    PS: And oh I forgot WLA fuel line disease.

    As faintly remembered http://forum.sscycle.com/viewtopic.php?f=6&t=12410, it is not easy to align the bowl where the float will not hang up on the bowlstem, without the shift rod hitting the bowl.

    Nearly all "sidebowls" were spec'd to have the valve indexed beneath the "Power" needle.
    Many WLA owners found their fuel lines and shift linkage demanded that the bowl valve be indexed perpendicular to the carb body, reducing the float 'offset' clearance dramatically.

    I assembled a couple over the decades, and I bet I abused them.
    Last edited by T. Cotten; 03-24-2020 at 07:01 PM.
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  3. #3

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    Before the lapping, I did the smack procedure lightly with a mini ball pien hammer on an anvil. Sorry I left that part out. Then came lapping until the needle would hang upside down in the seat while attached to a brake fluid vacuum hand pump. I pumped it to 25" vacuum whereupon it gradually leaked down to @ 1", stopped dead and hung there for 2 hours. It's currently in the test stand so stem not an issue yet. I've got a lot of time to devote to getting this to seal while seeking transmission parts worthy of installation (but that's another thread).

    I don't want to waste effort trying to achieve an impossible result and refuse to use a rubber tip needle. If you think a new needle and seat would be worth trying I'll include it in my next order.

    Not having good luck with repro parts.
    Last edited by Rex37W; 03-24-2020 at 07:17 PM.

  4. #4

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    I'd like it to hold this test at least overnight before installation.

    Thanks for helping out Tom, I enjoyed a visit with you at your shop @2006.
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    Quote Originally Posted by Rex37W View Post
    I'd like it to hold this test at least overnight before installation.

    Thanks for helping out Tom, I enjoyed a visit with you at your shop @2006.
    Having done that, over and over, Rex,..

    It becomes obvious the float valve was never designed to do the petcock's job.

    Leakage after an hour means somebody forgot to shut it off.

    ....Cotten
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    Last edited by T. Cotten; 03-24-2020 at 07:42 PM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

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    Thanks Tom, your assessment is all I need to continue with final carb assembly.

  7. #7

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    Flitz lapped needle
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