First, thank you for your time.I just bought a lower engine from thatsdax.com and then I bought a new piston as well because my old piston had an arrow shaped chip of metal missing from its top side. This will be a HUGE help guys, and I swear give me 1 more year and ill be a pro returning the favors! Below are all the factors I feel may be effecting this. The issue is that the piston seems to get stuck and locks the back wheel instead of turning over. I thought maybe some starting fluid, but that only works if the piston is moving inside. When I was trying to put the chain on the motor, I had to loosen the head bolts because there was to much pressure and it kept me from turning the bolt WITH the sprocket. Apparently there are quite a few different kinds of pistons though or its just a way for them to market. When installing the new piston and everything I only used a little bit of oil supplement to glide the piston into the upper engine.