a starter assembly for starting an engine is provided incorporating a mechanical diode in the drive train between the starter motor and the engine , including two coaxial plates with facing surfaces that are linked by pivoting members . the pivoting members are recessed into a facing surface of the first plate . they pivot outward under spring force from the facing surface of the first plate to engage slots in the facing surface of the second plate . this allows the first plate to drive the second plate , but also allows the second plate to overrun the first plate .