it depends 50cc goes about 30 mphon a flat surface 70cc goes about 40-50 mph 110cc goes about 50-60 125cc ill say 50 60 or mayb 70 mph
125
Chinese pit bikes on a smooth straight 120 km at the most
yes
Depends on the track, some tracks have a class for pit bikes to race in.
A net search don't show any "monter" bikes.
One can find pit bikes for sale online at various websites. One can find pit bikes for sale at websites such as Jazz Motorsports, PowersportsMax and Powersport Parts.
From 10 to 40 mph
a 125cc pit / stomp bike can reach limits of 70mph :)
pocket bikes are very fast. A 50cc pocket bike would bring you much over 30 mph and some pocket bikes can even go over 60 mph.
these bikes are often ridden around at drag strips and race tracks in the "pit."
Approx. 35 mph
It will at least go 45mph