Serious running probs totally erratic! air/fuel??

Discussion in 'Motorized Bicycle Trouble Shooting' started by motovator, Jun 1, 2012.

  1. motovator

    motovator New Member

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    This is my second build..this one isnt a new build like my other 66cc which runs perfectly now. I'm running an old used grubee. 6-8 yrs old?? Ran fine last year on a different bike. It doesnt have an NT carb or the new cns carb. I THOUGHT I had it built correctly on this build but when i ride it, it idles from extremely high to stall on stopped with clutch in. It will also seriously bog when throttle is eased up while riding, also accelerates on its own..sometimes..also will run perfectly at times once it somehow gets up to about 20 m.p.h. Choke makes difference but seems to run better at full choke than no choke or vice versa...theres NO rhyme nor reason to the running of this thing..ive tried different plugs..different gaps..different "pac man clamp settings...different idle screw settings and air fuel screw settings..etc. Can someone pleease give me a clue????? Thanx. Motovator.[B/]
     
    #1 motovator, Jun 1, 2012
    Last edited: Jun 1, 2012
  2. Al.Fisherman

    Al.Fisherman New Member

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    First of all a NT only has a idle screw adjuster.
     
  3. motovator

    motovator New Member

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    My bad..it doesnt have the NT carb. Not sure which 1 I have but its not the newest cns either.
     
  4. rustycase

    rustycase Gutter Rider

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    Hey M,

    Pics really help if you are not certain what it is that you have.
    I'll guess it's a cns v2 if it came off a grubee 48.

    It sounds like you have an intake leak.
    Which is likely, considering the age of the motor.

    Could be the intake seal, or the crankshaft seals.
    If it's not one or the other, it will be...
    Time is just not on our side, with any motor!

    and the carby is probably also gunked up a bit...

    You'll probably need to go through the whole diagnosis process.
    At least they are simple, and fun to work on! :)

    Good luck
    rc
     
  5. robbomberbomyea

    robbomberbomyea New Member

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    sounds like air leak to me,spray some wd-40 aroud the carb/intake conection if idle changes thats your prob. replace o ring between carb and intake. just pos your prob.good luck, peace
     
  6. BikeBerry.com

    BikeBerry.com Dealer

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    Honestly i would check first to see if your float is level, if it isn't level that will cause it to run bogged down. Also when you tune your carb make sure your engine is warmed up fisrt, if your in a high altitude i would start at the very top notch and work your way down, on the jet needle and c-clip, but if your in a lower altitude i would work my way up from the bottom notch. Also checking you jet for your gas line is good to make sure it is cleaned out and nothing is blocking your gas. I hope this advice helps! .trk
     

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