No mishaps wih bikes but I did once ( never again) change the cam belt on my Renult traffic. like others I was called in just as I was putting the pully back on. Whan I returned I tighend the pulley nut up, put all the other bits on and then tried to start it. It wouldn't fire up so I called the wife to start it while I took a look under the bonnet. It soon became clear that the pulley was not turning
STOP I shouted, but it was all invain I#d already done the damage myself. 8 Bent valves
The bloody woodruff key had slipped out and i hadn't noticed.
[Edited on 3-3-2006 by Jon]