Abstract: A motor speed changer for an electric motor wherein a mounting platform is mounted directly to the end face of an electric motor by means of special fasteners. The fasteners comprise cylinders having eccentric portions thereon which are rotatable and alignable with the ends of the through bolts of the electric motor by rotation of the cylindrical fastener. The mounting platform is provided with an integral bearing housing and bearing for rotatably housing a jackshaft. The jackshaft is connected to the output shaft of the motor by means of a two pulleys and a drive belt.