Just blew up the pic of your pinion. Although the resolution makes it hard to see as clearly as these dimming eyes would like, I think there are signs of tooth decay, probably beyond what the average motorbike dentist would be happy with. If there are any teeth, even just one, which looks more tired than the others, thinner, more pointy and less height, steps in its profile looked at side-on . . . . It's a sure sign of trouble looming.