400 ex engine problems

[GYOGI65]

400 ex
88mm 11:1 weisco piston and gasket
stage 1 hot cam
hd cam chain
PROBLEM :
ASSEMBLED TWICE AND first time valve lost keeper valve hit piston
had head done again this time valve retainer broke hitting piston
havent been able to get running long enough to get cam or rings broke in jetted carb but idle not good and top end rich any ideas want to stop putting money into head and into other things
this my sons 16th birthday presant and that was in feb

[nakomis0]

I don't know much about valves but, I do know they shouldn't be falling apart. Are they old? Sounds like you just need to get them all re done. The problem your having isn't common. Either they are old or the person doing thme isn't doing them right.

And of course your not putting the piston in the wrong way right. Cause that would cause the piston to hit the valves.

[GYOGI65]

PISTON IN ACCORDING TO WIESCO ARROW TO EXHAUST
SENT HEAD TO A MACHINE SHOP THAT DOES ONLY SMALL ENGINE WORK THIS TIME CYCLE ATV AND 2 STROKE