79cc vibration

Discussion in '4 Stroke Bicycle Engines & Kits' started by donb4103, Mar 21, 2017.

  1. donb4103

    donb4103 Member

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    I was wondering if anyone else has experienced this. I am building a 79cc bike. I`m using a Micargi GTS frame. Got it running and when ever you take off it shudders and vibrates like crazy until you get it up to a certain speed. It runs awesome after you get it going. But low speeds and takeoffs are really bad.
     
  2. donb4103

    donb4103 Member

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    It actually feels like the clutch is shuddering and only partially catching
     
  3. ultralight01

    ultralight01 New Member

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    Yeah, it's the clutch. A faster take-off would help you a lot. Also, a better quality clutch is good.
     
  4. culvercityclassic

    culvercityclassic Well-Known Member

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    Ultralight is right... nice rimes ha ha
     
  5. TheNecromancer13

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    Pedal up to like 8 or 10 mph, and then give it gas. Also pedal assist when you first give it gas.
     
  6. ultralight01

    ultralight01 New Member

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    Aaaaaaaaaaaaaaaahhhh
    Ohmygosh
     
  7. Wickedest1

    Wickedest1 Member

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    It is definitely the clutch. The engagement is somewhere around 1800-2000 rpm for most of the ⅝" clutches.

    Torque converter will smooth out your ride, but may decrease top end by a couple mph.

    I have no pedals on my 79 build and I've found that feathering the throttle up slowly will ease some of the shuddering.
     
  8. Kletus

    Kletus Member

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    I built a 79cc on a Macargi Huntington beach cruiser and it did the same thing. To remedy this I put a spring loaded chain tensioner on the drive chain and a fixed tensioner on the transmission primary chain. It now starts off from a standing stop with no problem. It wasn't the clutch in my case. My trusty Stromberg Carlson clipper speedometer says it will do 43 MPH flat out with a 44tooth rear sprocket. The 79cc four stroke will never be as smooth as a 2-stoke because it is firing to far below TDC at low RPM's. Mine smooths out at about 20 MPH.
     
  9. Tony01

    Tony01 Well-Known Member

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    Put the green spring in your max torque clutch. Locks up at about 2500.
     

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