Hi Robin,
Boy, I've been @ that place before, with chainsaws, car motors, transmissions and whatever. At which point do I replace this or that.
I have two of these two stroke engines but all two strokes are similiar. Still learning what I don't know about these chinese engines.
I think if I were to rebuild the top end on one of these things there are some considerations I would take into account. Rod and pistons slop at both ends and the condition of the cylinder itself. Any time you replace the rings you cross-hatch the cylinder. You want the new rings to "seat" or wear in. If I replaced the piston I would replace the wrist pin, stays and rings.
It starts to get complicated in a hurry for a straight forward job that seems simple. It all depends on the "wear factor".
Two thousand miles seems pretty good for one of these engines verses how much money you would spend in gas to make a car go that far. I've seen where you can buy just the motor for less than a hundred bucks. Not a bad deal considering the hassle of the rebuild and time into it. Then if something goes wrong your out your money and time. (experience speaking here)
I've only got a hundred and fifty miles on my 49cc engine and fifty or so on the 68.5 cc but am having problems already and its brand new. It seems there is always something to do on these engines.
RPM
RPM