I was riding a few days ago, stopped for a 5 min break, and when I was ready to go out again, my YZ125 wouldn't start, like it was flooded. I bump started it, it sounded rich for a while, then seemed to open up. I made half a lap before it stopped for good. No compression :( I tore it down, and a large chip was taken out of the top of my piston and ring on the exhaust side along with a hole in the side (not the top) of the piston just below this chip. Needless to say, I also had a good size gouge on the cylinder :silly: My question is why. Nothing had changed. The bike had been riding well, I hadn't touched the carb and the fuel was fresh. It was cool outside, but not cold. The piston was a little old (rings 10 hours ago, piston maybe 30 hours), but this looks more like detonation to me. Any ideas?