An electric motor has a wound rotor having a shaft, a rotor core, a commutator and windings wound about the rotor core and connected to the commutator. It has a stator confronting the rotor; brush gear connecting the commutator to motor terminals; first and second bearings for rotatably supporting the rotor, and an oil stopper fitted to the shaft between the commutator and the first bearing for preventing oil migrating along the shaft from the first bearing reaching the commutator. The oil stopper is of high temperature material, preferably a metal such as brass, aluminum and steel.