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Drip... drip... drip... from fuel petcock 83 XJ750 MMaxim

Discussion in 'XJ Technical Chat' started by Jiggs the Geezer, Apr 10, 2020.

  1. Jiggs the Geezer

    Jiggs the Geezer New Member

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    I have the fuel tank off the bike, took it off to drain it for winter storage. Last fall I noted that with the line off, and the petcock in the On or Res positons, the fuel drips very slowly. In Pri, the fuel piddles out nicely. Thats the way its supposed to work, when the engine is running and making vacuum, a diaphragm in the petcock pulls the petcock open and allows fuel to flow with the handle in the On or Res position. With no vacuum, no fuel is supposed to flow. None, not even that annoying drip... drip... drip...

    The question for other XJ'ers, can I buy a replacement petcock rebuild kit? Is it difficult to install? Does putting a kit in the petcock actually fix the problem, or should I just buy a complete replacement petcock?

    Theoretically, if the fuel leaks past the petcock into the carbs, the float valves should stop the flow at the float bowl level. But if one of those float valves leaks a smidgen, the fuel will overflow the carburetor, drain into the engine, equalize fuel to an open intake valve through the YICS channel, and drain into a cylinder, past the rings, and fill the crankcase with gasoline. That is all bad in many ways, I have a parts-bike to prove it.

    So I like having a petcock I can trust.

    Any advice from anyone on fixing a leaky fuel petcock?

    Thanks, Jiggs in Round Hill, Alberta, Canada
     
    Jiggs the Geezer, Apr 10, 2020
    #1
  2. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    chacal, Apr 10, 2020
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    jayrodoh likes this.
  3. cgutz

    cgutz Well-Known Member

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    Chacal's petcock rebuild kit worked great on my xj550.
     
    cgutz, Apr 11, 2020
    #3
  4. tabaka45

    tabaka45 Well-Known Member

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    I did mine 5 or 6 years ago and haven't had a problem since. Just be sure to follow the instructions in the the link Chacal gave you.
     
    tabaka45, Apr 11, 2020
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  5. Polock

    Polock Well-Known Member

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    mine did that, i took it apart and found a tiny grass clipping in it
     
    Polock, Apr 11, 2020
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  6. lostboy

    lostboy Well-Known Member

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    That happens when you steal gas from the neighbors lawnmower.
     
    lostboy, Apr 11, 2020
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