Scooterotica

my gp started to crap out at 3rd throttle, initially thought it was the carb, then went to check the timing, turned the flywheel and heard a scraping sound.

removed flywheel and noticed it had been scraping on the coils on the left side. the flywheel boss is off center!!!

i checked crank taper...ok and woodruff key...ok

tried to move crank taper from side to side to see if there is any play and i can move from side to side or up and down ever so slightly , possibly one fifth or one quarter of a mm, this is a 1 year old mec crank, is this just bearing play and acceptable ??

i've gotta change flywheel, and stator, question is do i need to change the crank??

if the boss was off center it would of rubbed from day one.. seems to me the crank has spun out mate..needs taking out the scoot and balancing..

and possibly a chance to get yer flywheel lightened / balanced too....

..........it was an af lightened flywheel!!!!!!!!

There is a little bit of play on a mag bearing if it has the correct bearing clearance which can be felt as a light movement.
If the crank webbs are out of line (needs trueing) there will be a witness mark on the inner bearing track which is seen as the inside edge of the bearing track and another on the outer edge of the inner track.

If the crank is running true there will be one continuous mark running evenly around the surface of the inner track.

The small amount of play is normal and if it was not there you would have worse problems once the engine warmed up.

I would think tarmac tickler was on the right track, the crank needs to be trued (not balanced). it should only cost a few quid

tzr.steve wrote:The small amount of play is normal and if it was not there you would have worse problems once the engine warmed up.

I would think tarmac tickler was on the right track, the crank needs to be trued (not balanced). it should only cost a few quid

IMO its no good just trueing it, if its spun on that pin then it needs a new [tighter] pin aswell, or it,ll happen again.

......ever since i put together i had a little scrape sound, similar to a flywheel just touching the cowl, i thought it was my kick start and never got round to checking,... just tried my old sil flywheel, re did the timing and it starts and revs smooth, a different scooter.

now if the flywheel before was not true and it has rubbed for 300 miles, would this then throw out the crank anyway????????

..took her out for a spin and she's going great, i'll keep a careful eye on it, if the crank was out would it affect the running, excessive vibration or something?, thanks for all the input

Vibration is usually a little worse than normal with a twisted crankshaft.