I opened up the head because it wasnt the woodruff key, Piston had a huge chunk missing out of the top. The Head is mint the piece went right out of the exhaust its still in my pipe. What can cause this so it doesnt happen anymore, 32-1 premium mix, tune was pretty good its in the shop if anybody can also guide me towards the piston and ring set because hes trying to charge 100 for a set i know i can get cheaper