I have a motobecane Moby X (similar to the mobylette) And well, I rebuilt the motor completely by guessing. The motor turns over and seems to be running OK.
When I was reading Fred's moped repair manual, I realized that I was supposed to line up the piston rings with a tiny bar on the piston itself.
I didn't specifically do this, although, it seemed to fit a certain way and I was able to put the thing in the cylinder hole. But the question is, would it even fit if I had put it in the wrong way? (Is there a failsafe?) Or could I have potientally screwed myself over?