Christini Technologies of Philadelphia, PA is planning to make their AWD technology available later this year. Christini makes both AWD bicycles and motorcycles.
The bicycles have a bevel gear and pinion driven off the rear wheel rotating a shaft which in turn is routed to and drives the front wheel. The motorcycle system is driven directly off the transmission. It transmits the power to a gearbox under the seat which turns a pair of counter rotating shafts traveling down the fork tubes powering the front wheel. The two counter rotating shafts eliminate torque steer.
The system is a posi traction type unit which delivers power to the front wheel when the rear wheel slips. The amount of power transmitted to the front can be adjusted from 50% to 90%.
Currently the AWD system is aimed at the enduro and off road markets however they say on road applications are planned for the future. They have received a patent on the setup and are now taking applications for pre ordering the units.