736 "overheating"

Spider: Hot roller pickups would signal to me that the motor is drawing a LOT of amperage. If the chassis & running gear is indeed free to rotate (no wheels dragging on the frame), I would take an ohmmeter and check the armature for any shorts to ground. Check each of the three poles between the copper armature surface and the gear shaft - it should show infinity for continuity.

You might also checks the brush length / brush spring tension/ and armature cleanliness as something is making the motor draw lots of amps to run.

I would start with the commutator.  Check the brushes, brush springs, clean the commutator and the slots, inspect the commutator to be sure there is not burning at the ends of the slots.  Renew the grease in the armature thrust bearings and get oil to the oilite armature bearings. Then take the rollers off and clean the shaft and bore and check that they are not excessively worn.  Look at the e unit fingers to see area are not worn or dirty and are making good contact.  It is a fine engine, probably just needs a little maintenance. Good luck. 

Thanks D&H and David - you were both right!

The brushes were worn and wiped. I cleaned the armature with contact cleaner, cleaned out the commutator and slots, armature bearings and the rollers - there was lots of cleaning to do.

Runs like a champ now - my dad would be proud.

Thanks,

Spider