Just a little bit faster...

[prodigit]

First of all, don't go WOT on an engine that is still in the break-in time.
You'll ruin the engine, giving it an early retirement.

it takes on average about 500 miles on city riding before the engine opens up a bit.
Do regular oil changes.
After a good 1000km the engine will feel much smoother, the sliders will wear some, allowing the engine to rev higher.

But 55-60MPH is about the max you can get out of a 150cc.

If your scoot recycles the exhaust gasses, get that EGR out, and re-jet your carburetor. Usually that could account for ~5MPH higher top speed.

Do one modification at a time, test thoroughly, and think before installing any other mod. Not all mods that are labeled 'performance' make your scoot run better.