top speed for a well tuned, stock china bike is around 35.
smaller sprockets and some porting, 40.
going all out, a few people have hit 50, but no one's been able to make it last.
the fastest china bikes at our races hit low 40's, 'cause they're geared for the corners more than the straights.
i've personally hit 62mph with a heavily modified china bike, in a full tuck, wind at my back, drafting a truck, on a long, smooth, straight section of the pacific coast highway.
i've got plenty of reliable witness who've clocked me over 50.
i also have boxes of destroyed pistons, scored cylinders, and useless chunks of chinese alloy to remind me of the futile attempts to make a fast chinese engine last.
if i paid full retail, i'd say i'm a few thousand dollars in the hole to achieve those speed goals.
my current cruiser takes me to work at 35 mph.