Welcome to MV.
Have a bit of a browse via the search function.
I found this, maybe of interest.
Has anyone kitted the S50?
I know plenty on here have done a 70cc kit and I think there may even be a 90cc kit (Malossi?) but 125 is probably too far for any 50 to be modified.
Also keep in mind any tax or legal/insurance implications of your mod.
Here in NZ if a modification is not declared it can completely void your insurance. 50cc scooters can be ridden with only a car licence and $100 road tax. Once you go over 50cc the tax hits $440
Good luck.