Buliding and electric vehical,,,, NEED HELP

hi,
am planning to make a electric scooter,,,something like SEGWAY scooter
am planning to connect the two wheels with a single shaft and wanna drive it wit a chain drive ......
am not able to get the exact motor rating for it some please help me...

the specifications are
two wheels connected to single shaft with a sporket mounted on the shaft
max.load 80kgs(human weight)+30kgs vehical weight
wheel dia 12"

please tell the the torque required to make it move and also tell the power required for the motor

thanks