I never had my DF topped out but have seen 75MPH indicated which is probably 68 or so real MPH after changing the sprockets from 13/45 to 13/33 and changing the high speed jet from a 88 to a 100.

These are 229cc push rod engined bikes so don't expect too high a top speed. Maybe 70MPH is the max and you don't want to stay there for long. Not an interstate bike. If you want higher speed then you need more motor.