A helicopter turbomachine includes an electric starter motor configured to rotate a drive shaft, a heat sink for cooling the electric motor, and a reversible ventilation wheel driven by the electric motor. The turbomachine also includes an overrunning clutch that transmits the torque from the electric motor to the drive shaft. The electric motor is configured such that, in the first direction of rotation, the motor rotates the drive shaft and the ventilation wheel to generate an air flow through the heat sink in a direct direction, and, in the reverse direction of rotation, the motor rotates only the ventilation wheel to generate an air flow through the heat sink in a direction opposite the direct direction.