Did my 66cc motor come with a 50cc head? Is yours like this?

The head gaskets are made of dead soft aluminum and are ment to be crushed with the proper torque. That band width is pretty narrow, though. Mime was around 4 mm on a 66 mm. The compression on a china motor leaves a lot to be desired so milling the head and removing the ring couldn't hurt. The head gasket would have a great deal of surface to spread the torque load. I'd advise a spray-on gasket sealer. I use Permatex Copper Spray-A-Gasket. Apply as advised, I've never had a leak.

And, really, taking off the band won't raise the compression much. You have to get pretty radical on a mill job on one of these for that to happen. To do that the best way is go to treatland and get the Puch Hi-Compression 70cc head. It's a dandy. $30. I don't know what they make it from but the cylinder head was clean, and I mean clean, and the piston crown had a thick layer of carbon burned on after running it for 3 months. The mounting holes are a bit off and need to be drilled out for an 8mm stud. The nuts need to be 13mm, you can not get a 14mm socket to go inbetween the fins. The sick bikes parts 8mm head stud kit has the 13mm nuts.