A motor bicycle control system is provided for controlling a motor for assisting rotation of a bicycle wheel. The bicycle motor control system includes a motor communication part and a first mode switching part. The motor communication part performs power line communication with an electrical bicycle component and that changes a motor operation mode of the motor. The first mode switching part is operated either by electrical power supplied via a power line through which the motor communication part performs power line communication, or by electrical power obtained from a generator. The first mode switching part switches the motor operation mode from a motor driving mode in which the motor assist in rotating the bicycle wheel to a motor power generating mode in which the motor outputs electrical power that has been generated using rotation of the bicycle wheel according to a state of communication with the electrical component.