Joe, I too have a machine (Singer 128) that smoked horribly. I didn't have time to deal with it but it freaked me out. I had visions of it burning the house down. I quickly unplugged it and put it back on its shelf with a note. i am surprised that everything checks out on yours. I just assumed that the wiring was bad or the commutator.
Rodney, so it needs to be replaced? What would be your guess as to what is causing this if everything appears to be good?