Some of these little bikes can do over 100km/h, 50cc water cooled engine making over 20hp at the rear.
And 40cc water cooled engines making 14 hp at the rear
How much clearance do you have between the forks' top tubes and the tank/frame on full lock ?
You may be able to cut/file/grind a couple of mm's off either side of the fork stop tab underneath the frame at the front to gain a bit tighter turning circle?
Brakes, they might be able to be upgraded by using copper sintered disc pads instead of the stock organic friction material pads
Also clean up any glazing on the braking surface of the disc with some 80grit dry sandpaper, that help's them to grab more.
stock disc pads on top, performance/sintered copper on bottom-