Don’t sweat the serial number thing…my 163cc GY6 variant also does not make any sense with the serial number. I think those numbers apply more to the generic Chinese 50 and 150cc true GY6 motors.
As Stig said, let us know your model of scoot. If you have a Kymco 125cc motor that is just a smaller bored version of mine (People S200) and will usually take the same clutch and variator as the other Kymco 125 and 163cc motors.