The 50 cc doesn't limit the speed to 30 mph. It's the way the fuel is
lead to and from it. And ofcourse the way all parts function together.
My puch for instance has it's original settings but does 35 mph anyway.
My honda c 50 does 41 mph.
And getting everything optimized will result in higher speeds.
A friend of mine has a hobby in classic racing in the 50cc range. His
Jamathi minarelli with moto morini engine does 109 mph (174 kph) and
with the new gearbox he's working on it'll do over 125 mph. My point, 50
cc wont limit the speed.
As a relative newcomer to the moped world, I'd like to hear more about moped
racing and performance modification. 100+ mph from a 50cc engine is
impressive. Are there places that mopeders get together to race? Sounds
like a kick and low $$$$ to boot. Any websites talk about this?