Jerks and jitters

Discussion in 'Motorized Bicycle General Discussion' started by tvc15, Aug 29, 2010.

  1. tvc15

    tvc15 New Member

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    The bike starts fast with choke on but needs to warm up a bit. Runs well and smooth but when I release the clutch the bike jerks and jitters until it gets up to speed, than it runs well as long as Im going 10 15 MPH

    When I reach a stop I pedal a bit to get it to a decent pace than back to the jitter for 1-2 seconds max

    Is this normal?

    1) 20-1 mixture with synthetic
    2) Boost bottle
    3) Bosh plug and boot with .038 gap
    4) Everything seems tight no noticeable air leaks
    5) performance exhaust
    6) Mount is rock solid- leaded handle bars
    7) 20 total miles
    8) Max speed was 28 MPH for a couple of seconds... not hot rodding

    Any thoughts?

    On a side note... Should I be using regular or r premium gas?
     

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  2. Goat Herder

    Goat Herder Gutter Rider

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    You are first gear. The engine will not take off by itself from a stop.
     
  3. tvc15

    tvc15 New Member

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    Im peddling to speed first, likes to do this til it gets to about 10-15 MPH
     
  4. timboellner

    timboellner Member

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    If you are really gapping that plug at .038 it's way too much.
    Try .024 and see how it does.
    The ignition is too weak to jump a gap that large.
    Tim
     
  5. PR3C150N

    PR3C150N New Member

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    Tidy Set up!
     
  6. Beej

    Beej New Member

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    I get the same type of issue in the "mid range" of the motor. If I am putting along it will gitter and jerk pretty bad until I get up to about 3/4 throttle then she gets going nice. I also peddle up to speed before letting the clutch out. Low to mid range she seems to be fighting.
     
  7. mapbike

    mapbike Active Member

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    The "jitter & Jerk" is perfectly normal at low RPM's on these engines, until the revs come up a little 2 smokes are pretty gutless but after the revs come up to the right point these little gals will start ginning nicely if the carb is jetted correctly and all else is right.

    Another thing to remember is that the size sprocket you have on the rear wheel will have a lot to do with how fast you will have to be going under peddle power before the engine will pull the bike on up to speed smoothly, (Example) if you have a 36T rear spr. you will have to peddle the bike up 2-3 mph faster to get the same take off results as you will get at a 2-3 mph slower speed with a 44T spr. I have 3 bikes one with 36T one with 40T & one with 44T, I have to peddle the 36T bike faster and farther before it will move on out smoothly, another factor is that you only have 20 miles on that engine so you have not even started getting her loosened up yet, so just keep running her right and when you have 200-300 miles on-r you will be much more pleased with how the gal goes unless you have a system failure before then but lets hope not.....just keep ridin-er and she'll get better & better the more you do.....

    Happy & Safe Ride-in
    Shan
     
  8. KCvale

    KCvale Well-Known Member

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    Exactly what I would I have said Shan, well done.
    With a direct drive you have no low gear, you'll be lucky to motor at idle through a school crosswalk without jitters, but you have a nice top end.

    There are ways to give you a better low end "stay alive" torque, but you sacrifice high end speed speed to do it for the most part unless you go extreme like an Expansion Chamber exhaust.

    Just for reference 'the bike' just really doesn't help with problems.
    Exact motor in this case really helps bud.
    There is a huge difference between a 48 and 66cc motor as far as low end for example.
    And then there is motor make itself but I won't go into that ;-}
     
  9. mapbike

    mapbike Active Member

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    Thanks for the thumbs up KCvale and nice work on those bikes, real nice.
     

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