I have gone through one horrible expeirence. It started three months ago when i hopped on my wr 400 and tried to start it, but there was no compression. After disassembling the bike I found sunflower screenings and a mouse nest in the pipe(no silencer). The cylinder was full of it to and i have no idea how. anyways it was a mess bent valves messed up seats and an ugly piston. I ordere a wiseco high comp piston. and took the head into TWISTED Wrist motorsports. bad bad bad idea. Got head back the first time reassembled, and no compression. Checked with carb cleaner all the valves leaked. Sent it back. this time told them to double check it. 1 week later pick it took it home. checked. 3 valves seeped. took at back again. Found out the machine guys pilot for the cutter was wrong. got it back still leaked. took the head apart and my valves were cut into OVALS. Took it back again got all the valves replaced. Then i was told the problem was the lathe chuck wouldnt go small enough. Reassembled. It still leaked took it back this last time and it held liquid. So i just reassembled it for probably the 7th f'n time. ITs been 3 months of hell. the only reason i didn't take to someone else is that the shop kept paying for their screwups untill the last time, and every other shop in bozeman was busy. Now i just let it warm up, then shut it off.let it cool. then took it for a gentle drive. Going down the road it randomly made a metal nasty seizing sound and killed the motor. Went to kick over and everything still moved smoothly. Started it again drove a ways and it made the same evil squeel death moan and stopped the motor. Still kicks over easy after pushing it a mile home. and starts Its the weirdest thing ever. Any ideas. Any questions.I tried to be very carefull on the rebuild but that many teardowns might have caused me to screw somthing up. Please help me. by the way its not my first rebuild I ve got 4 bikes 2 sleds and a 75 poncho motor under my belt. I think im going to go drink drano.