is well known in the art two sets of two brushes 22 and 23 fig4 held by respective brush holders 24 and 25 are juxtaposed to the commutator 18 at its outside circumference the brushes 22 and 23 are pressed against the contact pieces 21 of the commutator 18 by coil springs 26 fitted to the opposite ends sides of the cylindrical yoke 13 are a front cover 27 fig2 covering the left side of the yoke 13 as seen in the figure and a rear cover 28 covering the right side of the yoke on the figure collectively forming with the yoke 13 a motor case indicated generally by the reference numeral 29 the starter motor output shaft 17 is journalled for rotation on the front cover 27 and the rear cover 28 respectively by bearings 31 on the rear cover 28 fig2 and 4 is provided a positive terminal 32 for power supply from the positive electrode of a battery described later by reference to fig5 mounted on the vehicle the positive terminal 32 is suitably connected to the brushes 22 on the positive electrode side the brushes 23 on the negative electrode side ground side are connected to the end closure 28 by grounding fasteners 33 the motor case 29 is grounded.