[cayuse]

Size has something to do with it, too. At max speeds your drag coefficient is going to matter a lot more than your mass. If you are heavier it will take longer for your 20hp to get you up to speed but if you are taller in the saddle and lighter then that max speed will be less, because of the extra wind drag from the taller rider. Pete, I think you'll find if you could put 50 lbs of lead in your tank bag you would still hold 70mph because your wind resistance won't be any different, yet your 'weight' would be 200lb.