This might have nothing to do with your buddies bike, but I have a story....
After a hard high speed highway ride, the nut came loose on the rod going through my PAMCO assembly (washer+magnet+circuit board), causing the magnet to fall off when the bike was parked (tilted). At the time I didn't know and when I tried to start it, of course it wouldn't. Switch the ignition "off" and BOOM.....backfire louder than gunshot at point blank. So loud someone called the cops!
For whatever reason no matter how tight I turn that nut, every few months it will come loose again. I think because the spin of the rod is not opposite of the way it loosens, eventually it unwinds itself loose. I know that's not supposed to happen and I'm sure it never happens to anyone else but I live with it
So when I try to start and it backfires this is how I know my PAMCO nut is loose