I don't think the piston would have kicked over if the rings had come out of the groove. I'm assuming you didn't have to "force" anything together when you slipped the cylinder over the piston and rings?

If you stand the 3-wheeler up and remove the pipe, you should be able to look into the exhaust port and see if the rings are still free.

By chance is the wear you are describing on the exhaust side of the cylinder?
This is the side of the motor where most of the heat is sustained. If so, it could have happened during idling for too long.

Also, during break-in, you are supposed to let the motor get cold to the touch before putting it through another heat cycle.[img]i/expressions/face-icon-small-wink.gif[/img]

 

Thanks 2fun, that seems to be the culprit for the cylinder wear. If I remember correctly, it is very close to the exhaust port. I had to twist the cylinder to one side a little when I put it on, but didn't "force" the cylinder over ths piston. It moves up and down freely, so I'm not really worried about it.