I'm about to embark on a new cam chain installation on my 426, along with an 03 exhuast cam. I'm thinking that since I'll have the top end mostly apart, it wouldn't be too much extra effort to replace the piston, rings, wrist pin, and bearing. Is this good practice or overkill? I've heard many reports of YZ 400/426 owners replacing pistons and finding out that the original is still intact. On the other hand, I've read many posts where people swear by top end rebuilds every few years just to be safe. I have an 01 YZ426 that's all original and according to the guy I bought it from it hasn't been ridden hard. It never had the top end apart and never had the valves adjusted. I checked the valves when I bought it in December and they're still within spec (although they're close to the minimum allowable). This leads me to believe the guy I bought it from, that it hasn't been abused.