Reviews I've looked at show the top speed as 78 MPH, but note vibration is a significant issue above 60 MPH. Rider comfort is also an issue at that speed, given the upright seating position and lack of a fairing (but that's not unique to that bike, and an aftermarket windscreen would solve it entirely).
There are better-performing 250cc bikes. That said, for what it is, it's a nifty little machine.