I have a similar motor on my 31-15 (which sounds fine) and the information I found said that the motor had packed bearings. As far as I recall, this is oil-impregnated wool that is packed into the motor to deliver lubricant. I'm sure after 70+ years, it has solidified into some kind of varnish, and wanted, as you do, to put fresh lubricant in the motor to ensure a long life. The only advice I could get was some version of "If it ain't broke, don't fix it" which I found unsatisfying. I turned my attention elsewhere (found a treadle table for a 31-15, which I highly recommend) and the project is "on hold." I'm at work now, but when I get home, I will send you any information I have accumulated in a PM.