My morini m01 engine was running. It would run for about 15 minutes and then stall. I checked the compression and it was around 80 to 90 psi. I ordered a piston and rings from a Garrelli that matched the measurements of my cylinder. The bike ran okay for a few miles then died. Compression is now minimal and the top of the new piston is black with carbon. What did I do wrong and how do I fix it?