My '99 yz400f is running absolutely fine, but I've read where some people are replacing their piston for no apparent reason. I'm a "B" MX rider with many hours on my bike (approx. 200 Hrs). The bike doesn't smoke and there is no loss of power. I recently adjusted my valves for the first time no problems. My question is, are some people been experiencing piston failures (i.e. cracking or siezing)or are they replacing the piston for the heck of it.