426 overhaul gone bad

[EXrider65]

Rebuilt the ol' 400 with a 426 kit 13:1 JE piston and so on. After 12 - 15 hrs it started to smoke,so we tore it down and the piston broke up both sides right over the rist pin (both sides) up to the 2nd ring. Ran like a champ no noise, no loss of power, just smoked. Can anyone give ant info on this.

[rooster300ex]

How did you break it in??

[EXrider65]

rode pretty easy never got into the rev limiter, it never got hot or was ran hard. Just average trail ride couple blast but nothing crazy.

[RiderTRX400ex]

what were you running for fuel? also, was your stock sleeve bored for a 426, or was ti resleeved?

[2004exrider]

I'd personally call JE myself and explain to them the problem.

Jimmy

[JasonP]

sounds to me like the engine was detonating.. but JE could also be at fault here. I would for sure give them a call. What kind of fuel were you running?