[Lilbrandon]

Hi out there I have a 2006 crf250r just rebuilt everything wiseco crank,piston,rings had kibblewhite valve ground and seats motor had about an hour- hour and half on it and it locked up took apart every things totalled when I first took head off both exhaust valves where broke of and in bottom of motor both intake valves looked fine does anybody know why this would happen thanks in advance I'm new to site but if got some great info from everybody on here thanks

[JimDirt]

Welcome to the site !!

When you say valves ground and seats ... what exactly do you mean ?? , did someone grind the new valves ?? (thats a no no) , did a reputable shop that does dirt bikes cut the seats ??? , there are lots of reasons this could happen , but the most likely suspect is the valve keepers were not installed correctly , or the shims were installed incorrectly and the keepers popped out and the valves hit the piston and snapped off .... or the valve seats were cut incorrectly and cut too deep and the springs did not have enough tension on them to hold the keepers in place and the first time the engine was revved high they popped off and the valves hit the piston , .....

In any case , if the valves hit the piston you can kiss the rod/crank goodbye , as the bearing is damaged from the impact and you will have a rod knock if you put it back together without either replacing the entire crank/rod , or having the crank redone and a new rod and journal on the crank installed

More detailed info is needed .......