It was so easy, you only had to modify the variator (the automatic transmisión of the scooter) because the limitation was just a low gear that didn’t let you go faster (think of driving always on first gear). You removed a stop on the variator that let you use the full range and the limit was gone.

Anyway, 2 stroke motors were also easily tunable, and people used to change the escape, carburetor, even sometimes the cilinder was changed to have more power on those little machines.