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  1. #1

    Default Ironhead fast idle

    1972 has extremely fast idle in neutral but when I am in first and let the clutch out about half way so Iím just about to roll the idle drops down to where it should be. If I let go of clutch so Iím rolling idle goes back up way high

    Keihin butterfly carb with 80 slow and 160 main, idle screw all the way out so that doesnít help. Mixture screw wonít slow idle will only cut out.

    Iím going to check for intake leak but Iím just wondering how and why the clutch is affecting idle speed

    No gauges so Iím just going by ear

  2. #2
    Senior Member

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    Join Date
    May 2011
    Posts
    859

    Default

    Hi Cooldean69,

    Welcome on CC, you should do a little intro here to start, it's great if you introduce yourself a bit :

    http://www.chopcult.com/forum/showthread.php?t=96

  3. #3

    Join Date
    Jan 2016
    Posts
    233

    Default

    Letting go of the clutch puts load on your motor and the idle won't give enough fuel to keep it going like that.
    Sounds like you could benefit from rebuilding your carb, if you don't have an intake leak.

  4. #4
    Sugarcubes
    Guest

    Default

    disconnect your throttle cable from the carb and see if it starts. It might be you have kinked it or its snagging somewhere, causing your throttle to stay partly open.

    If this doesnt make any difference, it sounds like an intake leak and you should inspect / replace the seals at the manifold.

  5. #5

    Join Date
    Dec 2018
    Posts
    1,955

    Default

    The other consideration not mentioned is a bad or failing mechanical advance unit, if the motor is so equipped.

    Symptom points to a vacuum leak or advance unit. Classic.

    Jim

  6. #6

    Default

    Thanks guys

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