ok this isnt normal

Discussion in 'Motorized Bicycle General Discussion' started by bulljo, Oct 26, 2013.

  1. bulljo

    bulljo New Member

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    Ok i just replaced my crank bearings and i have the following mods... ported cylinder, ported intake, shaved head, hp airfilter, ported banana pipe, petcock from a moped and a 36t sprocket on 26inch wheels. I run octane booster and b8hs plug gapped at .025 and with the carb tuned all i get is 30 mph from her. And theres this knocking at top end maybe this crank is a dud or the timing is off or is it possible for a banana pipes silencer cones to get plugged? Shoot some suggestions guy ill do anything. Btw theres no leaks.:-||
     
  2. ddesens

    ddesens New Member

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    I would pull the head off and check the top of the piston edges for shiny spots where it is hitting the head possibly. Happened to me a few times. added an extra head gasket to compensate. It would restrict your engine rpm's if its hitting.
     
  3. crassius

    crassius Well-Known Member

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    without knowing your skill level, I'd first suspect the crank is out of true
     
  4. mapbike

    mapbike Active Member

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    does it have lots of vibes at the top speed of 30mph?

    If so crank being poorly trued and seriously out of balance could be the problem as has been mentioned but also since you say you shaved head down piston hitting head could also be an issue if head was shaved down to far for being used with one head gasket as has also been mentioned.

    My question is, have you run this engine combo in the past before the main bearing change?

    if so did it have a top speed higher than what it currently has?

    Map
     
  5. Huffydavidson

    Huffydavidson STREETRACER/MANUFACTURER

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    or it could be destination your hearing .
     
  6. rogergendron1

    rogergendron1 New Member

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    i get 35mph on a 44t with a puch head heavy porting, port matched, piston ramps, skirt cut for intake, cns v3 carb, and a free flowing pipe.

    your probably not tunned right ... i need to see a pic of your motor and a pic of your plug.

    i need your motor size and type also

    does it vibrate a lot or is it smooth ?

    also what carb do you have ???

    it sound like (without knowing all of this info) that your carb is out of tune and you have a air leak somewhere !and also despite popular myth the higher the oct the cooler it burns the higher the comp the higher the oct needed ... adjust plug to warmest you can run with the comp and and octaine lvls you are running to get a full clean burn.

    ohh and your plug is too cool try a b5 or 6hs, despite comon myths higher octain burns cooler than lower octaine !!!
     
    #6 rogergendron1, Oct 27, 2013
    Last edited: Oct 27, 2013
  7. bulljo

    bulljo New Member

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    Heck yeah theres vibes its more of a rattle then a vibration at top end but it sounds like it revs as high as usual with the clutch pulled in but only goes so far when i ride. Ive ran this crank and mods before no prob and got at least 40. I changed the carb for a spare i have and no difference. Its a 66 cc and the wrist pin sits lower on the piston. Ill check the piston for marks get a fresh gallon of 91 with a dose of motorcycle octane booster and also a hotter plug. Oh yeah the magnet moves a hair back and forth cuz the woodruff key is smashed so ill fix that and change my petcock for the orignal one as this is my first time using it.
     
  8. FMB42

    FMB42 New Member

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    How did it run before you modified it?

    Did you do one modification at a time, a few at time, or all of them at once?

    If you did more than one or two mods at a time, your chances of knowing what's wrong is greatly decreased.
     
  9. rock out

    rock out New Member

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    I can only get to 36 km/h and around 40 if I pedal hard with it
     
  10. mapbike

    mapbike Active Member

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    Lol........! Destination. .....!

    Map
     

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