I have an older Athearn F-7 that was an Ebay purchase and turns out that the motor is nearly shot. She runs ok but runs extremely hot. We are talking painful to touch the motor hot. I have repeatedly cleaned the commutator but every time I run it again it turns it black with some pretty thick crud like what often collects on the rails after running too many old cars with plastic wheels. The Loco does not have flywheels and seems to not have any wieghts either. Just a die cast frame, Motor, U-Joints and gearboxes. All the wieght is in the frame it seems. I need some advice on how to best handle this. Please keep in mind I am not made of money and would have a hard time even scrounging up 30 dolars to buy a rebuild kit. Is there anything I can do using the stock parts to help keep this old girl alive and pulling frieght? Or is she destinied to be a yard ornament?