Centrifugal vs. Clutch Engines

Discussion in 'Motorized Bicycle General Discussion' started by Wood.Neely, Feb 12, 2011.

  1. Wood.Neely

    Wood.Neely New Member

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    I bought a Grubee Skyhawk 66 cc with a clutch about a year ago and loved it until it decided to completely break down... probably my fault because it was a guinea pig motor amongst some others...

    now, after receiving an e-mail with a coupon code for $50 off i am thinking it's time to make the new investment.

    my question is, has anyone had a grubee centrifugal clutch engine, and if so how we do they work? the clutch engine started just about every time, but i felt like there was a lot of extra stress on the engine, mount, and bike frame... that being said, theoretically a pull start should alleviate a majority of my concern, but i need to hear some good things about it before i make the purchase.

    please pass on any info. about the pro's and con's of either engine and i'll keep posting what i decide to do and then can make judgement of my own.
     
  2. professor

    professor New Member

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    I do recal seeing that nobody can seem to find a pull starter that won't break right away.
    Once a cent. clutch locks up the stresses are the same.
     
  3. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    Another thing to consider is that if the pull starter breaks, there's no way to start the engine! :(
     
  4. Bob Mac 18704

    Bob Mac 18704 New Member

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    You can bump start any motor with a centrifical clutch, the same way you would start a motor with a hand clutch.
     
  5. Greybeard

    Greybeard New Member

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    This is true if equiped with a centrifical clutch that has a "one way" bearing. The kits that come with 4 cycle engines don't normally have that bearing in their clutches and you can pedal forever without turning the engine over.
     
  6. Bob Mac 18704

    Bob Mac 18704 New Member

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    This is also true but I think he was refering to the two smoke motor. If I'm wrong then I appologize for my ignorance
     
  7. Wood.Neely

    Wood.Neely New Member

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    yea bob, i was referring to the 2 stroke... seems like there isn't much good to say about the centrifugal other than it will still work if part of it breaks (that's not too convincing).

    thanks to all, more advice is always welcome
     
  8. Sideshowbob

    Sideshowbob New Member

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    Since the quality of materials in these kits is not that great; I think fewer parts= simpler is better. Less things to break or fall off. New pads for a regular clutch are$7.50 and a whole new gear with pads is $15. I think I'll stick with the simpler clutch design. I like the pedal start and once I'm idling I keep the motor running at stoplights etc.
     
  9. Greybeard

    Greybeard New Member

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    Sorry for the misunderstanding on my part. When "pull start" was mentioned, my old brain went to 4 stroke.
     
  10. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    You cannot bump start these motors with centrifugal clutches!!!, & I know of no one way bearings for any of them that will allow you to do so.
     
  11. madwheels37

    madwheels37 New Member

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    Do you HAVE to have a pull start with the centrifugal clutch assembly? I have a 66cc bump start, and would like to switch to a CC cause of all the stopping and starting I have to do in town. So would i be able to just get the CC part and not the pull starter? I have been told so, but then again how fast would you have to pedal to start the motor? How exactly does that work? You pedal fast enough that the weights go out and turn the crank? Also i feel silly, but the motor continues to run while having it stopped right? Like you pedal start it, then it's running until you hit the kill switch?
     
    #11 madwheels37, Feb 14, 2011
    Last edited: Feb 14, 2011
  12. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    Yes, you must have a pull starter with a centrifugal clutch.
    Centrifugal clutches are what our old skool mini bikes & go-karts with lawn mower engines had on them.
     
  13. madwheels37

    madwheels37 New Member

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    So no way to start even on 2-stroke without pull start?
     
  14. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    No way that I know of... :(
     
  15. kerf

    kerf New Member

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    I've heard much about the pull starters being crap. Just what parts usually fail and could one adapt parts from a quality pull starter to work?
     
  16. LS614

    LS614 New Member

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    I think that everything in the pull starters has broken on someone at some point. I hear bad castings, the handle and rope snapping of, the starter pawls breaking and other things. If you made one with quality internals and a machined billet housing it could work (Creative Engineering or Pablo should really get cracking on a U.S. made starter ;) ) But no, there is not a single one that is really known for good quality. Now to answer a different question, you can bump start a centrifugal clutch by jamming a ring of leather belt between the bell and the pads. This is dumb because you lose the entire point of it being a centrifugal clutch. And finally, in response to Sideshowbob, there are WAY more parts in a manual clutch than a centrifugal. Were it not for the bad quality of both the starter and clutch, this would be an EXCELLENT idea. Hope this helps :)
     
  17. madwheels37

    madwheels37 New Member

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    My thoughts exactly, couldn't one just put a quality pull start or rope/handle assembly to make it better?
     
  18. fritzalee

    fritzalee New Member

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    FIW I have a centrifugal clutch installed on a BGF 2 stroke, with the SBP shift kit, no pull start, works ok. The motor started easier with out the shift kit, but with some effort it starts just fine. This CC was purchased from Zoombicycles.com, their web site doesn't show it now, the only troubles I had was with the covers being to close, corrected that with some corn flake box gaskets for spacers. Now adding the SBP kit required their longest bottom bracket, a bunch of spacers for the jack shaft, and modifying an old front derailer to keep the chain on.
     
  19. Bob Mac 18704

    Bob Mac 18704 New Member

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    Let me say this again. You can bump start any of these cent. clutches on a chinese 2 stroke. The one way bearing is included in the cent. clutch itself. We may be talking about 2 different clutches but the ones you buy on these sites for $29.00 to 59.00 will bump start.
     
  20. adam valentine

    adam valentine New Member

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    I own the grubee cent with pull start and I can NOT bump start it i have to pull start it and yes pull start broke right away so i replaced with one from lawnmower and no more problems
     

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