piston, valves, or both!?

[rtrocket59]

after racing at a gncc my motor was shot, i had smoke blowin out the exhaust, oil leaking out of the very top seal and the bottom of the top half of the cyclinder. before i stopped racing the quad would run fine until high rpms than it would just bog out and shut off and sometimes make a clicking noise. is it the piston, valves or both?

[Kovatch]

I had issues with my 2003 Z years ago. I had P&P, vavle job, stage 2 cams, big carb, hi comp piston, etc. It would not roll through high RPMs no matter how I jetted it. I ended up having worn out valve springs, which caused the valves to stay open too long and whacked the piston.

Can't provide you with too much insight, but if you blew the motor, you probably have a laundry list of parts. Depending on the year, I thought people were putting DRZ springs in the heads as they were a little stronger?