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Thread: Vacuum leak?

  1. #1
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    Default Vacuum leak?

    Back here with the leak still, wondering if a vacuum leak can happen on other spots than the intake boots. I have good throttle response and the
    de-acceleration of the rpm is also quick, no hangs when it does want to work, but when it doesnt it hang close to 4000rpm.

    Asking if theres any other spots because for my airbox I use a thick plastic cable tie to seal the two airbox pieces together, you cant find a quarter inch thick hose clamp anywhere and the OEM part is $100, But, if that's where im having sealing issues, than its $100 well spent.

    Also can it be the joint that is meant to seal the airbox pieces together, mine I can move up and down and side to side while it's in place, so maybe the rubber has shrunk overtime?
    Last edited by timebombprod; 03-04-2021 at 05:13 PM.
    Ian

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  2. #2
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    Can you post a good clear picture of the area you are thinking is a problem?

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    Close up of the area, ziptie is supposed to be hose clamp and the rubber seal is easily moveable when the two pieces arent together. Snapchat-541523295.jpg
    Ian

    1982 GS650GLZ

    Want a "twin" for my bike

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    Heres a farther view better showing where I'm talking about Snapchat-1328864403.jpg
    Ian

    1982 GS650GLZ

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    Yes, pretty much anywhere rubber meets metal or plastic has the potential for leaking.

    I've seen worse clamping methods, but that definitely has the potential to pucker the rubber and cause a leak. The clamp itself should only be around $6.00
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    Quote Originally Posted by BigD_83 View Post
    Yes, pretty much anywhere rubber meets metal or plastic has the potential for leaking.

    I've seen worse clamping methods, but that definitely has the potential to pucker the rubber and cause a leak. The clamp itself should only be around $6.00
    Luckily found a site, but it's coming from europe, better than the 130 they want from Japan.
    Ian

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    Want a "twin" for my bike

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    One other place to check is from the airbox to the carbs and make sure each boot is securely attached. Not just snug but completely on the carb intakes as the older the rubber the more likely it will shrink

    Cowboy Up or Quit. - Run Free Lou and Rest in Peace

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    Quote Originally Posted by cowboyup3371 View Post
    One other place to check is from the airbox to the carbs and make sure each boot is securely attached. Not just snug but completely on the carb intakes as the older the rubber the more likely it will shrink
    They're holding up good, but yes they are shrinked a bit. They are fully secured but i do have to put them on a certain way, start with pushing the 3rd boot all the way on from inside the airbox, then tighten, then I do boot #2 the same way securing the 2 inside boots on, and then 1 and 4 go on no problem.
    Ian

    1982 GS650GLZ

    Want a "twin" for my bike

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    If you still have an air leak that is causing the hanging revs or racing it won't be on the inlet side of the carb.
    It will only be between the needle jet and the inlet valve.
    Additional air in those areas will weaken the fuel mix, causing it to lean off making the fuel burn faster and in turn causing the revs to rise.
    This is the same conditions as when the engine will race just as you run out of fuel when stationary.
    An air leak on the inlet/airbox side will have the opposite effect and cause bogging but it will have to be more than just a small gap.
    The inconsistency you describe points to fluctuating problem which may not be a vacuum leak at all but something simple as an intermittent sticking throttle mechanism or frayed cable.
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    Quote Originally Posted by zed1015 View Post
    If you still have an air leak that is causing the hanging revs or racing it won't be on the inlet side of the carb.
    It will only be between the needle jet and the inlet valve.
    Additional air in those areas will weaken the fuel mix, causing it to lean off making the fuel burn faster and in turn causing the revs to rise.
    This is the same conditions as when the engine will race just as you run out of fuel when stationary.
    An air leak on the inlet/airbox side will have the opposite effect and cause bogging but it will have to be more than just a small gap.
    The inconsistency you describe points to fluctuating problem which may not be a vacuum leak at all but something simple as an intermittent sticking throttle mechanism or frayed cable.
    Oof, this is tough. I've disconnected the cable and gave throttle from the rack itself and still had the issue, but the rack seems to go back in place fine.

    This is a bummer lol.
    Ian

    1982 GS650GLZ

    Want a "twin" for my bike

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