I have about 1000 miles now on my 80cc, I generally run a 32:1 oil (STILH fully synthetic), and 93 octane fuel. I also run it at the medium jet position on my NT stock carb. My bike for the past 50 miles has made a pinging noise at medium and high RPMs, which leads me to believe it was spark ping. Took the head off, plug was fine, but there was so much carbon build up it was unbelievable. I put a new (aluminum?) head gasket on, and tried to run it again. Same issue, pinging noise. I feel as if when I put the head gasket on, it shifts so slightly when the bike is running and nicks the piston as it goes to TDC, which is causing the pinging noise and rough idling. Could this be a leak? Bad piston? Rings?