I have a Babylock 418 three thread I bought new in the 80's? Maybe a little earlier, and they can be wonderful and if your sewing clothes with cotton a must have. Do the blades need to be replaced? Do the feed dogs come up and move? You may need to clean out a lot of lint and threads. Is it threaded correctly? that can be a pain in the hinny, but once done usually works good.
Will be looking for more info, wish I could get my hands on them, but threading is very important.