Originally Posted by a1fa
This bike will have no problem riding at 60mph for extended periods of time -- granted you have a 400 or 426 motor with upgraded crank pin. What this motor needs is a bit more oil (add an-inline radiator) to avoid more frequent changes, and extend oil life.
With higher gearing the motor will not spin as much, but it will also not be fun off-road. My gearing is at 15/47. Works decent for street hooliganism and off-road shenanigans.
In 5th gear, at 5950 out of 8500 RPM - you are looking at 60mph .
The motor should last you as long as same vintage TW200, or XT225.
Gearing and oil is the key to making these motors last.
Oil is cheap insurance change it often!