One of the biggest problems that previous attempts had was fitting motor, transmission, and batteries (old car batteries or marine battery) within the limited space of the motorcycle frame.
I tried to apply for a grant to develop a new electric motorcycle a couple of years back given new developments in lithium batteries and electric engines that are high torque/high horsepower that will fit within a motorcycle rim.
Wouldn't you know it that the Gov't said that there weren't enough advances in the technology to warrant a $20K grant!

There is a firm in China that just recently decided not to sell their electric cycles/scooters here anymore because of litigation. Seems that even if crashing an electric scooter is exactly like crashing a motorized one, because it's a new machine the lawyers were hammering them saying the product was somehow defective in that it allowed the rider to crash.