Hi, have recently bought a non-running generic Chinese 110cc pit bike.
Got it running after finding out that the cam timing was out. However after riding for a short while, the bike stopped, with the timing out again.
After messing with this a few times now, finally took the ignition/coil plate off to reveal the chain tensioner & the crank mounted cam chain sprocket. Turns out the sprocket is moving on the crankshaft. Taking the sprocket off I couldn't immediately see anything to stop the sprocket rotating on the crank...am I missing something? Should there be a pin or a woodruff key?
...& the crank mounted cam chain sprocket. Turns out the sprocket is moving on the crankshaft. ....
i had an impression that the sprocket is Heat shrink fitted into the Crank axle. difference in diam for heat shrink is summink generally speaking 0,05mm.
it deffo isnt a Conical cone fittment. i havent either seen any w-d-key locking.
sounds like you need to buy a new Crankshaft assembly.....
Thanks for the response, that is what I thought, and confirmed today when I had chance to take it apart in the garage.
Had a go at drilling a well in the sprocket and crank, and putting a weld in. My welder is a bit lightweight for that kind of job, but it's not as if it can make the situation any worse.
If it doesn't hold I'll get a new crank.
How did you know the alignment for the Sprocket Vs TDC Bigend gudgeon pin, or how would i say it in english...
can go wrong by anything from 0~1 teeth...
i assume you didnt just spot weld it in random fix location....
would need basically a Mint Crank alonside to see the exact "alignment". unless its a 1 teeth exactly pointing at Gudgeonpin.. 12'o clock vertical cylinder or 9'o clock horizontal laydown cylinder, how do i say it in english...
I'm afraid I didn't do anything clever. I aligned the sprockets correctly before dismantling the cam sprocket. As the sprocket on the crank end was only moving when under load, I just then hoped it wouldn't shift whilst I drilled the well, then welded.
Fortunately it didn't move, and I've ended up with it being all lined up pretty well.
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