Auto store, tube (smaller than tooth paste tube) of lithium grease. Car Oil, drained from used quart containers (left over a funnel all night) to fill a little squeeze bottle. Find some felt and place over the armature shaft and oil. Never in excess. You can use a q tip to apply the grease. I have not known the grease to be destructive to plastic.
Found an erector set nut on a switch today, been missing for a year. The 2036 with magnatraction found it and shorted the roller to the frame. hwell:
Engine is fine.