Many years ago I had a Norton ES2 with a straight-through exhaust so it sounded more throaty than this clip. Unfortunately a valve-guide disintegrated and bits of it bounced around inside the cylinder causing a fair amount of damage as you might imagine. It was easy to work on though.
I can't remember what happened to it, but I think in the end the gearbox seized and I had to ride it most of the way back from North Wales in first gear. After that it wasn't worth repairing, but ironically it probably would be now.