Abstract: A bicycle has an auxiliary engine, a wheel, and a clutch mechanism disposed between the auxiliary engine and the wheel for enabling and disabling power transmission between the auxiliary engine and the wheel to select one of a pedal-propelled drive mode and an engine-propelled drive mode of the bicycle. The bicycle includes a clutch lever for connecting and disconnecting the clutch mechanism, a throttle lever for controlling a throttle valve of the engine, a switching mechanism for connecting the clutch mechanism in coaction with the throttle lever when the clutch mechanism is disconnected, and an engine starting circuit closable and openable in response to connection and disconnection of the clutch mechanism. The clutch mechanism can be connected in response to operation of the throttle lever, the engine can be started when the clutch mechanism is connected, and the engine can be rendered inoperative in response to operation of the clutch lever.