Besides the obvious, (bike chassis, motor and controller) what's needed is an adequate amount of energy storage for the job. Depending on the speed at which the 50 or 60 miles will be covered, that will vary. Perhaps someone could post some motorcycle energy consumption figures to help you make the calculation. I would guess 8 kWh might be adequate.
Popular DIY batteries include Thunder Sky (now Winston Battery
) and (Headway
). There are a few other battery possibilities as well.