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Discussion in 'Motorized Bicycle General Discussion' started by granpaj, Aug 7, 2009.

  1. granpaj

    granpaj New Member

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    Re; 80 cc

    Clutch drive gear and magnito drve gears failed. After replacing both gears I think the timing of the gears is not properly set.
    The engine will run , but it apears that timing is off ( fireing too early )
    Any help will be appreciated.
    Thank you
    granpaj.shft.
     
  2. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    Why do you think it's firing too early?
    Replacing both of those gears would not change the timing.
     
  3. granpaj

    granpaj New Member

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    Thank you for your reply. During re and re of both gears the crank shaft and mag shaft was possibly out of proper timing ( that is my assumption ) while trying to start the engine it is kicking back on the first rev, plus not able to get max rpm.
    any recomendation is welcome.
    granpaj
     
  4. 2door

    2door Moderator
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    I'm not sure what you mean by "magneto drive gear" The mag rotor, (magnet) is attached to the end of the crankshaft. There is no gear involved. On the right side of the engine is the primary gears. The small one is attached to the crankshaft and it meshes with the larger one that via the clutch and a countershaft drives the sprocket on the left side. Replacing the gears on the left does not effect the location (index) of the magneto rotor so ignition timing is uneffected by gear location. Did you have the magneto coil off the engine? It can be installed backwards but the magneto cover will not go back on if you did. Can you post a photo to show which gears you replaced? Also we're assuming your engine is a two stroke.
    Tom
     
    #4 2door, Aug 7, 2009
    Last edited: Aug 7, 2009
  5. granpaj

    granpaj New Member

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    Hi 2door Re 80 cc
    Correct me if I'm wrong the clutch assembly is attached to the crank shaft, the clutch gear drives a smaller gear ( both gears on the right side ) that turns the magnito ( via a shaft ) on the other side of the engine (on the left side ) I have replaced both gears on the right side
     
  6. granpaj

    granpaj New Member

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    Sorry Tom
    No pictures at this time

    John
     
  7. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    Here is your correction-

    The clutch assembly is attached to the output shaft.
    The smaller gear is attached to the crank and drives the clutch assembly (larger gear).
     
  8. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    Have you looked at the mag end (left side) to see if the anything has moved?
     
  9. leftywoody

    leftywoody New Member

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    A kickback sounds like the timing is advanced a tooth or so
     
  10. Norco John

    Norco John New Member

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    A "tooth or so" HOW? the magnet is keyed to the left side of the crankshaft w/a Woodruf key, not gears. If ignition timing is suspect, then I'd check to see if the key has sheared. I've seen this many times on lawnmower engines, especially after somebody tried to take the top off a rock.
    :-||
     
  11. granpaj

    granpaj New Member

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    I thank you all for your help

    Granpaj
     
  12. Junster

    Junster New Member

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    Just incase GranpaJ you still are wondering. The small right side gear is on the right end of the crankshaft. The spinning generator magnet is on the left end of the crankshaft. The timing is controled by the magnet. There is a key slot in the magnet that keeps it positioned for the timing. Check that Key if the timing seems off. The gears on the right side just drive the clutch shaft, they have no affect on the timing. How old is your motor? Those gears seldom fail.
     
  13. granpaj

    granpaj New Member

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    I thank you for the info, yes you are right (at my age I'm still learning.) I only had this
    80 cc for a short time , on the second run with in 5 miles or less there was some major crunchis happened from the engine, when I got it home I remooved the clutch housing cover there were 2-3 dozen tiny ballbearings , the clutch gear and the smaller gear was badly damaged. After strugeling to remoove both gears I thought since turning those shafts I possibly got things out of time. How ever the engine at this time is runable how ever it kicks back on the first turn or so , and it seems it will not reach top RPM
    I thank you verymuch for your info again your explonation has being the most clear and simple, and correct.You have no Ideal what different opinions and recomendations I received.
    granpaj
     
  14. Junster

    Junster New Member

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    Try to get a look behind the small gear at the case seal. Make sure when the metal was flying around in there that it didn't damage it. Also once the motors get run in a little you usually need to re-torque the head. Try a few squirts of wd-40 at the carb and intake tube mounts. If the idle slows you found a leak. Sorry your clutch bearings scattered.
     

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