[rambo]

Also be aware that a failing main bearing will cause the rotor to rub on the stator. Not so likely but it happens. You would have heard a grating sound when running though.

 

[rambo]

When my rotor contacted the stator, the main roller bearing had started breaking up. The rollers had lost a bit of surface and was chewing away the outer track. I could hear the grating noise of the stator rubbing so went home slowly . Not an alternator fault but the rotor had a bit of metal missing. That alternator was still usable after the rebuild of the engine.
I doubt this is what caused the failure on the op's bike, it was a noticeable noise.
My rotor and stator seems to last a very long time. Replaced one stator due to the centre getting loose and another had lost magnetism. Never bought new parts as i have original items bought from autojumble.