How did this happen?

Discussion in 'Motorized Bicycle General Discussion' started by \./, Mar 16, 2013.

  1. \./

    \./ Member

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    Heard a loud grinding noise, turned the motor off then tried to start it back up with no success, opened clutch cover and viola...
     
  2. \./

    \./ Member

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    fried smalll wheel
     

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    #2 \./, Mar 16, 2013
    Last edited: Mar 16, 2013
  3. Allen_Wrench

    Allen_Wrench Resident Mad Scientist

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    I think Norm or Tom or some of the more experienced builders on here could give you a better answer, but "mechanical or manufacturing defect" is the first thing that came to mind. If one gear had a weak tooth, that'd break some time, then with the aid of momentum the engine would strip the rest off, I imagine. Or if something were to make your rear wheel seize solid and the chain held, you MIGHT get a stripped gear like that.

    I think the important question is: would it be cheaper to buy a new China girl? Or is it safe to fix this one?
     
  4. 2door

    2door Moderator
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    Did you ever lubicate those geras? They look dry from your photo.
    How many miles on that engine and was it noisy from day one?

    Tom
     
  5. Maxvision

    Maxvision New Member

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    Did you look to see if either gear still had it's woodruff key in the keyway? If either gear was ever taken off and put back on, the woodruff key might not have stayed in the keyway and spun out once you got to high speed then lodged between the gears. Only other think I can imagine is a washer or something was left behind in the clutch case and got caught between the gears or one gear tooth broke off and stayed between the gears causing a chain reaction.

    Those gears start as powdered metal I believe. Might have been a defect in manufacturing.
     
    #5 Maxvision, Mar 16, 2013
    Last edited: Mar 16, 2013
  6. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    I've never seen that before!!

    It's easy to replace the gear for around $15
     
  7. \./

    \./ Member

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    no it ran smooth since day one, this engine has roughly 150 miles on it, this is my "around the neighborhood" bike. about 2 miles into the ride today, i heard the grinding for the 1st time and quickly turned the engine off. inspected what i could without any tools then tried starting it up again with no luck, it just didnnt engage. i ive never taken the clutch or the crankcase apart so im assuming the woodruff key didnt have a chance at coming out. looks like all i need is this: http://www.bikeberry.com/engine-kit-parts/crankcase/small-bevel-wheel.html to make it run again.
     
  8. \./

    \./ Member

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    and yes, i lubricate it / grease it every 50 miles or so
     
  9. Maxvision

    Maxvision New Member

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    Hey Yuri, did you check to see if your piston seized? oh wait...if piston seized you wouldn't have spun off the teeth on the small gear...well maybe it could if it seized for a second, broke a tooth then broke the rest in a chain reaction. Will the bike roll with the clutch pulled in?

    Can't see from the picture but is the machine screw still in the clutch adjustment nut on the outside of your clutch plate? Is the inside of your clutch cover scored from the adjustment screw grinding on it?
     
    #9 Maxvision, Mar 16, 2013
    Last edited: Mar 16, 2013
  10. Toadmund

    Toadmund New Member

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    I was thinking about that same theory, a crack in one tooth, it broke and the gear teeth clashed and broke the rest.

    To the OP, were there chunks, bits, or dust on the bottom of your gear case?
     
  11. \./

    \./ Member

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    nah its not seized, i can manual turn it over.
    the machine screw is still in and tight. the bike rolld with or without the clutch pulled in
     
  12. Maxvision

    Maxvision New Member

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    Another one of the Universe's mysteries I guess. Kinda like why does a ketchup bottle have a neck so skinny you can't get the ketchup out laff

    Before you send off for a gear see how thick the keyway is. Some motors have thinner keyways. Or bring the gear over, I'm sure I have one that will fit.
     
    #12 Maxvision, Mar 16, 2013
    Last edited: Mar 16, 2013
  13. \./

    \./ Member

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    fits like a glove, thanks Scotty
     

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  14. Maxvision

    Maxvision New Member

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    Not a bad deal huh. Pack of cigarettes to get your bike running dance1
    <wheeze...cough, cough>
     
    #14 Maxvision, Mar 19, 2013
    Last edited: Mar 19, 2013

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