i have an 08 base model and stock gearing was 14-42, i have a gps but never clocked it but if i were to guess it would be around 72-75 mph on flat black top road with 20in tires, and thats bouncing off the rev limiter.
my ds650 at 9500rpm with stock gearing and 20in tires did 83mph, but it took some motor work to get it to rev that high