Been racing the kx250f off-road since the '06 came out. Overheated the '06 twice because of blowing anti-freeze in the 3 hour race and plastic Y-connector meltdowns but no piston cracks (probably because of replacements due to overheats. '07 bike ran fine until the hot start stuck open on the starting line, the bike went maybe 5 minutes and cracked the piston just like this one. '08 had approx 5 hrs on it when it cracked the piston down the center this past weekend in Kentucky at a MidSouth race. Hot start was well maintained did notice a slight knocking noise in motor when cranked on choke at high idle before the race. Get this! I am using Wiseco piston in IceCube 276 big bore kit from Max Power Engines on both '07 and '08 bikes. Spoke to Cliff at MaxPwr, they have worked with Kawasaki, Wiseco & ProCircuit to determine that at certain RPMs the piston can actually slap resulting in a cracked piston. He said this is caused by the KX ignition system. Bottom line, barring a stuck hot start sucking cold air, your piston could last 5 hours or 50 regardless of whether it's stock or Wiseco. In case any GNCC racers are reading and care I've learned that using EvansCooling.com NPG-R coolant (372 degree boiling point) and the Boyesen Quickshot or QS2 (cranks hot) go a long way in making this bike that was designed for a 30 minutes moto last for a 3 hour GNCC assuming you don't get a randam cracked piston. Sorry for the long rant! Hopefully this helps someone!