Well, if anyone wonders if semi fluid grease gets to every part of a Burman gearbox, having just spent 2 hours cleaning it out, IT DO.
No lumps of metal found from the damaged gear, but if you like metal coffee i can supply lots of 'grounds'.
I had a thought about worn splines and loose sprockets. If a replacement output gear is not available would an epoxy repair like JB weld or Loctite 660 do till a part became available.
I know that this is ok for keyways. I would certainly try it on my bike if i had to. The tricky part would be in making sure that the epoxy would not get into the gap between the output gear and the bearing spacer. Lightly oiling the sprocket 'should' stop the sprocket sticking to the epoxy..