Need some help, first motorized bicycle

Discussion in 'Motorized Bicycle General Discussion' started by ncoop, Aug 5, 2012.

  1. ncoop

    ncoop New Member

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    So I have my first MB, its a grubee skyhawk gt5. I want to tune it and I am having some problems. First, sometimes when idling it will go absolutely crazy, and I will not be able to shut it down with the kill switch, second, how do I adjust the idle and air screws on the carb (its a CNS), and finally when I twist the throttle towards myself it sometimes with shut off and sometimes it will rev higher. Also what happens when a cable is bent I would much appreciate some help.

    :-||
     
  2. bluegoatwoods

    bluegoatwoods Active Member

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    Re: Need some help, first MB

    Let's see.....if you have throttle cable that is really crimped or damaged in some way, then that could cause the symptoms you mentioned. Then your only way out is to get a new cable.

    If that's not the problem, then I'd have a look at the slide inside the carburetor.

    Also you'll do well by reading these posts. A lot. You'll find the answers that you need sooner or later and you'll also pick up answers to questions that you don't even know you have yet.

    Best of luck with it.
     
  3. ncoop

    ncoop New Member

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    Re: Need some help, first MB

    The clutch cable is the one that is crimped, thanks for the other advice, would changing the idle screw make it idle at a lower speed?
     
  4. GearNut

    GearNut Active Member

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    Re: Need some help, first MB

    The idle speed screw would not need to be changed, only adjusted. Turn it in to raise the idle, turn it out to lower the idle.

    A few threads that may interest you:
    Inside the 2010 Grubee Skyhawk CNS Carb
    OMG I have to tune a CNS!!! Help
    cns carb spacer
    Click on them to read them.

    As for a crimped or sharply bent clutch cable, that ruins it's ability to operate smoothly and may cause it to hang up or get stuck. It also increases the effort required to operate the clutch.
     
    #4 GearNut, Aug 6, 2012
    Last edited: Aug 6, 2012
  5. Allen_Wrench

    Allen_Wrench Resident Mad Scientist

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    Re: Need some help, first MB

    Or...you might try an "NT Speed" carburettor. A little less to tinker with, and still loads of fun.
    The CNS carbs can be pretty good from what I've read, but most everyone seems to agree that they can take some getting used to. If you like to tinker and tune, the CNS is what you want. The NT Speed carbs are decent performers (I have one) but their strength lies in the fact that, once you get them set up how you like them, you can leave them alone. They seem to require a bit less attention and fiddling with.
     

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