The big wheel version's i would expect to hit around the 65-70 mph mark.
60 -65
stock it will go 60 to 75 but with a pro circuit fat pipe it will go 60 to 80
As fast as it can.
i got mine to go 95
if it has pro circuit racing parts 2 stroke it goes 60 to 80 mph
about 90mph :)
70
as fast as you want it
the kx is faster
40 mph
Not aware of a KX300.
75 to 85