I don't know what one is either but here are a few suggestions
Check the exhaust. This is the easiest place for them to restrict your moped. Did they weld a washer in it?
If it is like a honda, they will put a plate with a star shape on the clutch to keep the clutch from engaging completely. You can tell that by looking at the clutch. There will be pins in the clutch that spread out to the ends of the star shaped plate when the clutch engages (you cannot see them engage because the engine has to be running) If this is the case (that means if you have a honda scooter) just remove it.
For any other suggestions, it would help to know exactly what a ch50 is. If it is one of those new scooters with a funny name then it may be exactly like some of the models that would be familiar. (what kinda motor Suzuli, Honda, Yamaha and such)