You can drill out the rivets to get to guts of the motor then check out Darth Santa Fe - YouTube and Harrison at SMT Mainline on repairing/tuning up old, poorly working locos. You then drill and tap the places where the rivets were and resemble the motor with screws
My mantua tyco 4380 is barely running. i didnt know where to start taking apart the motor because it's riveted shut So I tried lubing up the axles and gears and it runs hesitantly. The headlight do illuminate for some reason but i suspicious it may h burned out. I also having a hard time figuring out when it was made.