Having 5 playmobil old style electric trains, two of them the double motored 4052, I need to learn how to dismantle and service the motor blocks to make the trains run more smoothly. Two of the engines are a little jerky, I've cleaned the tracks and picks ups but no improvement. The newest of my engines run smoothly so I guess it's the motors. Do I just go a bit crazy and wd40 everything? Any tips greatfully received, even if just being pointed in the right direction. A photo walk through would be the dream!