A couple of points on this problem. The valves don't "stick". When the cam drive system breaks, either the gear goes or chain , whatever, the cam stops turning in synch with the pistons and some of the valves will be held in the open position. The valves then are bent as the pistons keep moving past. I would definitely want to see the piston crowns when the motor is apart as they WILL have contacted the valves. The other point is that the sprocket was updated on later engines though I have no idea whether this improved the failure rate. My bike was recently into the dealers for the paint can rattle (again) and the mechanic removed and tightened the tensioner manually and the rattle has disappeared for now but they wouldn't do any further work. My bike is a very early '05, approximately 12th off the line with 36,000 kms on it. I intend to replace the gear myself over the winter with an updated piece just to be sure.