in my experience 60 hp is only good for just about 200kph not sure taller gear will achieve higher speed.

My Triumph D6 would reach 150 mph indicated but on GPS only 135 mph (216 kph) Ducati 900 with only 80 hp but being narrower and more aerodynamic was good for 220. RG500 nearly pegs the needle (250+ indicated) but on GPS only about 220 and that's with about 100hp at the wheel