After buying this quad from a kid I bought a book and re built the quad. But since I've blown a head gasket. Now I'm looking at the piston inside the head sleeve and the back end of the piston is hitting the head causing a gauge in the top head. What would cause this? And does anyone know how I can fix it? Please help I'm going crazy! !

 

I would either assume your rod bearing is done for if you didn't rebuild the rod or the more likely than not answer, the head was shaved at one time for higher compression and you probably need to go back to a stock style head. The previous owner might have used a thicker head gasket too.

 

Also, make sure you installed the base gasket to the cylinder