crankshaft spinning freely???

kavid2012

kavid2012

New Member
I was rebuilding my engine today and i was tightening the nut which holds magnet in place. and as i tighten it harder the the whole crankshaft will start to rotate, so i have put screwdriver between the gears on the other side(clutch gear and engine gear) so i can thighten harder.
and as i tighten the nut harder it kept spinning and spinning
and i checked the other side and the screwdriver is still there and holding the gears from turning so i was what the **** is going on?
and i found out that the crank shaft on the magnet side is spinning off the crank.
and i was like what the **** ? should it do that???
i don't think the other side crank would spin like that then the whole engine won't run, lucky it is magnet side... though i'm scared that it will happen like that for the other side too and the motor will be just spinning by itself and won't pull anything.
I don't know really...
if the magnet side crankshaft should spin freely like that...
it's still kind of tight so only way you can spin it is with the nut and the wrench...
but i'm kind of worry that it will get loose and won't spinn the magnet either
i understand the magnet is light so they might not have put no key way to hold the shaft with crank, but i think they should've put key way anyway
what do you think???

by the way has someone disassembled the crank?
 

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I don't really have an answer to your question, I've never disassembled a crank, but neither side should spin like that without the whole assembly turning. Are you sure its not just the nut turning (stripped?) with the shaft remaining stable? If the magnet side has turned then the timing will be off...
Maybe someone that has pulled apart a crank will chime in, I know there are a couple different versions, some with more pieces than others... And a whole new crank assembly costs about $18 bucks....
I've got a bad habit of torquing the he!! out of things, which is bad news on these china girl motors. I went ahead and purchased a compact click style torque wrench to keep myself in check. It has a dial to select the torque you want to achieve, when you reach that torque it "clicks" and you know to stop. It's not much larger than a regular socket wrench, that wrench and blue loctite is keeping my bike together nicely...
Good luck with your crank.... (wait a minute, that don't sound right.... lol)
 
here is story why this happend...
when i disassembled the crank, i hit the shaft with hammer (which made crankshaft bolt thread smooshed or flattened ) to take the crank out of the case.
and when i tried to assemble it back together, the nut wouldn't go in to the bolt because i flattened the tip of the bolt with hammer.
so i filed the tip of the bolt little bit and put other nut(8mm x 1.0mm) which i think it is the same size as the original nut but twice thicker
and it went in very tightly as i tighten the nut on to the bolt and i think the thread was little damaged and caused a lot of friction and i kept turning in and it was very hard to turn with the wrench, and i think that forced crankshaft spin off the crank...
and as you said i think the timing is messed up since i moved the magnet key way position... i think i will have to buy a new crank and becareful not to hammer the tip next time...
 
Crank is only $18 bucks, it's the shipping that gets ya... The whole bottom end is $74 for 66cc and $64 for 48cc with free shipping over $50 on parts at gasbike.... (you can get free shipping on a bottom end, but not a complete motor or kit, go figure)
 
I think your hammering and forcing the threads has created the problem for you, I would say just chalk it up to experience and get a new crank or bottom end....
 
lol i'm sorry it was clutch spinning....
i thought the shaft was rotating but it wasn't.
and the magnet keyway is exactly at 25 degree off to the rigfht from the TDC.
 
kavid2012 said:
lol i'm sorry it was clutch spinning....
i thought the shaft was rotating but it wasn't.
and the magnet keyway is exactly at 25 degree off to the rigfht from the TDC.
Click to expand...

Thought you had the small bevel gear locked with a screwdriver??? At any rate, glad it seems to be ok and hope you familiarized yourself with your motor a bit....
 
kavid2012 said:
actually i held the output sprocket with chain on it.
Click to expand...

Well, next time try posting the truth so you can get the best help possible here. Clearly above you posted that you jammed a screwdriver between the small and big bevel gear to lock the motor instead of using the chain as you indicate today. I had a sneaking suspicion that there was some misinformation here, cause I have never read about this particular problem before. That's why one of the first things I said was "are you sure..."
Good luck with your motor, hope it all works out well for you...
 
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