Idle Screw Adjustment

Discussion in 'Motorized Bicycle General Discussion' started by Hicksy, Jul 9, 2008.

  1. Hicksy

    Hicksy New Member

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    Looked around the site to find an answer but no....

    I've read and heard that the screw has to be out 4.5 turns. While fiddling around with it (trying to get the motor running smoother) I noticed that the only effect it has is increased revs from out 1 turn to fully shut (all the way in). It's a new engine.

    What effect does this screw have and why would it only work out to 1 turn?

    Should I adjust it within that 1 turn range?
     
  2. stude13

    stude13 New Member

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    hi; you are right 4 1/2 out until later. it does not set the idle, it is adjusted at the top at the cable end. much more knowledge here. good luck. mitch
     
  3. deacon

    deacon minor bike philosopher

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    After you get the cable length adjusted correctly the idel screw will actully do something.
    Run it out to 4.5 turns then adjust the cable length to where you want it to idle. From that point on the idle screw should work fine.
     
  4. Pablo

    Pablo Master Bike Builder & Forum Sponsor

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    Indeed it's a sign that something else (cable adjustment, air leak) is not correct.

    Adjust the cable so there is just a tiny amount of slack in the sleeve (you know it's too tight when turning the bars changes idle speed, too loose when the twist throttle doesn't return (it'll be funky too tight as well) ).

    Assure you have no intake leaks....use water or WD-40 or propane gas cautiously around the fittings, see if idle changes....

    And bare in mind, idle can be funky until well broken in. It will change a lot as engine warms up.
     
  5. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    You are incorrect sir!

    The screw is for idle speed adjustment ONLY. They tend to be different lengths, so if you have it at one turn and it idles good, leave it there.

    The adjuster at the top of the carb is for taking the slack out of the cable. You should adjust it until there is just a tiny bit of free play in the cable housing, then adjust the idle speed screw at the side of the carb.
     
  6. misteright1_99

    misteright1_99 New Member

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    All the idle screw does is hold the slide slighty open for idle, the farther in the higher the slide, the higher the idle. You should not use the adjustment at the top of carby for idle adjustment. As Joe says this is strictly for taking the slack out of the cable. 4-1/2 turns out is just a general starting point each engine will be different.
     

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