When the old piston went bad it broke above the exhaust port.Most of it got above the piston and went up in the head.Their was a piece i couldnt find.Split the case it wasnt in the bottom of the motor.Well i put it back together and then i got my head back threw the power valve in and move it .The spring moved and power valve didnt but i didnt really check it.Just felt the spring move didnt watch it from the bottom and put it back on.When i took it back off that piece of piston was behind smashed  it.So i took it back of and grind the piece out which i thought i got it .I put it back on and it still hung up.So i took it off again and really took my time grinding and polishing it up.Now it work great and the bike runs great.I need to throw my 38 pwk and get
 a better pipe for it to finish it off.Saving my money for a new paul turner mid range pipe.