Lionel has acknowledged a problem with the design of these engines and has a technical bulletin out that discusses "uneven operation in forward and reverse." I recently took one in for repair that would not go in either direction. Lionel described the problem as a loose bearing plate that housed the lower end of the armature - this one was tight. However, the field structure plate, which is staked on in four places, was loose. This caused the field to move and bind on the armature. I restaked the plate, reassembled the engine, and the owner said that it has never run this well.