the small cog in the engine broken

Discussion in 'Frame Mounted Engines' started by iron_monkey, Jul 27, 2007.

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  1. iron_monkey

    iron_monkey Guest

    My bike is now as if the clutch isnt even making contact(but the clutch is working fine).

    The problem is that the small cog(where the giant slot screw is and next to the big clutch cog) now cannot mechanically connect to the engine crankshaft.

    All i want to know is, how is this thing normally supposed to mechanically connect to the crankshaft?

    Is there a 'slot' in the axle hole of the cog that slows it to drive the crankshaft? (in my engine there is a slot in the cog but no 'pertrusion' from the crankshaft to meet this slot)

    edit: I also discovered a 'slot' in the crankshaft, if that helps.

  2. azbill

    azbill Active Member

    there is a key that locks the drive sprocket to the driveshaft...just like lawnmower
    sounds like the key got sheared off
    it is a 3/16 woodruff key you will need
  3. iron_monkey

    iron_monkey Guest

    Thanks for your reply.

    We fabricated our own peice of metal from a bench grinder.

    I find it improbable that the metal would snap under the forces. The bike was also slowly slipping more and more until it couldnt move me.

    More likely the metal wasnt installed in the first place(if it snapped the characteristic imo would be catastrophic failure instead) and was relying on the press fit of the cog on the shaft.
    Last edited by a moderator: Jul 28, 2007
  4. srdavo

    srdavo Active Member

    are you talking about the cog on the clutch side? or the cog the drive chain runs on?
  5. iron_monkey

    iron_monkey Guest

    Well I said its the small cog next to the big clutch cog, so its on the clutch side.
  6. gone_fishin

    gone_fishin Guest

    i see you posted that you fixed it & i was wondering if you ever found out what actually happened? did you find any evidence of the missing/broken key?
  7. iron_monkey

    iron_monkey Guest

    I want to know for sure what actually happened too. I couldnt find the key, only metal shavings from the cog slipping on the driveshaft.

    In the post above I gave what I think is the likely cause.