Gearing is probably one of the most important things to do. not only the countershaft sprocket but the rear sprocket as well. If you are not using first and starting out in second then you obviously have the wrong gears on the bike. Possibly a different pipe and check your jetting. Also, tires and tire pressure play a very important role in performance.
the ktm 65 sx goes 60mph and its faster then the other 65s
85
55mph
there is no such thing as a yz 65 there is a kx 65 and a rm 65 and a ktm 65 but no yz 65
faster than a ktm 65sx !!
ktm dont suck they got all hydraulic clutches and brakes so who put that is dumb. a ktm 85cc will go bout 65-70.
With stock gearing 65-70 mph
Faster Than a cheetah on steroids.
kx 125 is better because KTM 125 or any ktm snap so go with kx 125
Its more than likely the transmission
With stock gearing around 60-65 MPH.
It goes 63-65 kawaski is better I have a kx 80 and it goes 75 with my procircuit pipe 67 without it