125cc to 150/160cc upgreade

[Leiberg]

Hi guys! I have a 125cc, and i'm looking for just a little more power so i can keep up with the traffic better. What is the best way to do that and still keep it reliable? i was thinking of putting a bigger bore kit on (150cc or 160cc) and maybe some of those Dr Pulley sliders/rollers on. Would that give something more? I can get it to about 52 mph as it is now (bone stock) on a straight flat road. I would love to hit about 60-65 ish.

I may need to mention that the bike is pretty much brand new. Only got 350 km on it (218 miles) and its a Gy6

The engine type is a 1p52qmi