I've got a 50cc that's been around the block a few times, actually several times. Hadn't flown it in a while, just noticed two things I think are related. It doesn't like to be at idle, doesn't run all that well and dies sometimes, harder than it should be to start. Also it has lost a good bit of compression. Can hardly feel it. So are these two things related? I'm figuring just put a new set of rings in her and she should be fine. /Thanks.

PS: If I put new rings in her, do I need to go back to break-in oil?

The worn rings and the poor running characteristics are related

The new ring(s) will seat in again in short order

Pull the top off and see if the ring(s) is stuck on the exhaust side of the piston. If so, pull the piston and do some ring and ring groove clean up. If the engine was not run real hot the ring will prolly still be good and regain the compression seal after all the carbon that wedged it into the ring groove is gone. Not all that often new rings are required. If you have 400-500 hours on the engine and the end gaps are wide, then you probably do, but generally no.