This is where Chinese engines shine...dollars per horsepower and dollars per mph.
Like kirrbby said, be careful. The stock rolling chassis is marginal above 50mph. Above 60mph, things start to change...rapidly & dramatically...it's basic physics. At 50mph, the dynamic forces will be ~75% greater than they are at 40mph and the curve is logarithmic(!). The brakes start losing effectiveness around 55mph, the stock shocks will bottom-out easily, as will the fork. Over anything but billiard-table smooth pavement, K0 pogo sticks are the stuff of white-knuckled nightmares, at high speed. Most tires available carry a "J" (62mph) rating. Knobbies, at freeway speeds, no thanks. I've experienced 80mph+ on a very well setup CT70. The last time I pushed that far was before this web board existed. Not trying to piss on your parade, only give you some advance info on what to expect. For the occasional short blast, the tires will live, engine braking can be used - quite effectively - to yank the bike below 60mph, before grabbing a handful of front brake and finding a stretch of smooth pavement, free of side streets + intersections, becomes far easier.
I strongly suggest making sure that the brakes, bearings & tires are all in tip-top condition. The rear shocks should be upgraded to something with spring rates that match your weight. If they're bottoming-out, they're dangerous; eventually, you'll bend, or break, a shock mount. If your fork is K1-later, learn how to "oil tune" it; that makes a huge difference. And...when it comes time for new shoes, road tread improves handling & stability. Getting a passable 50mph cruiser doesn't have to cost much.
IOW..."keep the shiny side up".
