What happen

well i did my rebuild this winter. did everything buy the book. Took it out ran it about and hour to break it in. did some kinda hard riding for another hour or two.

I took it out the other day and was riding pretty hard. and i heard something in the motor. so i pulled in the clutch and pushed the bike back home took the valve cover off and i see my intake cam has scratches on the lobs and then look harder and all my intake valve caps are all broke. my valves on the cam side are all messed up. so i took the head off and there are marks on the piston. It is a 2006 yz250f. i put in a 08 piston and reshimed the valves and put them back in speck what did i do wrong or what went wrong. i just dont get how the timing could have been off if i ran it for 4 hour with no problems. and it went up the the rev limiter a couple times with no problems.

How many hours are on the bike? The valves and springs might have been too tired and you got valve float. Has the bike had the recall on the valves done?

maybe you slipped the cam gear???

well i did my rebuild this winter. did everything buy the book. Took it out ran it about and hour to break it in. did some kinda hard riding for another hour or two.

I took it out the other day and was riding pretty hard. and i heard something in the motor. so i pulled in the clutch and pushed the bike back home took the valve cover off and i see my intake cam has scratches on the lobs and then look harder and all my intake valve caps are all broke. my valves on the cam side are all messed up. so i took the head off and there are marks on the piston. It is a 2006 yz250f. i put in a 08 piston and reshimed the valves and put them back in speck what did i do wrong or what went wrong. i just dont get how the timing could have been off if i ran it for 4 hour with no problems. and it went up the the rev limiter a couple times with no problems.

Been there done that with the kids 07. Valve float will cause the piston to hit the valves. With his bike it broke the center intake valve. Send the head off to jesse williams and he will fix it. He put lighter retainers on the valves to help stop this issue and his prices are very competetive.

Sorry and Good Luck:thumbsup:

there are about 60 hours on the bike and the springs have never been changed. yes the bike had the valves changed for the recall. i will take a look and see if the cam did slip and see if it is off and let u know on that. and dose jesse have a web site the i can check out to see what all he does thanks for all the replys

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