I installed a 70cc Airsal on my Tomos A55 at the end of last season. I followed the recommended break-in routine and the bike was running fine except when I let off the throttle, I was getting a strange jerking forward motion along with a chirping sound.. I thought that the revs might be too high and that I needed to adjust the timing?
Well today I decided to give the bike a going over before summer season and I pulled off the cylinder to see If I could spot anything. The metal head gasket was partially torn off and after de-carbonizing the piston head I think I've spotted pieces of the gasket melted into/onto the piston. The rings are fine and everything else looks ok, aside from a couple scores in the cylinder head.
The only thing I can think of is that the piston might have been pushing out too far and hitting the cylinder head? Does that even make sense, or is it just the head gasket breaking that's the issue? Would a thicker cylinder gasket give me the correct clearance if it is indeed the piston?
Thanks for the help!!!