Terry's site for slant-o-matics and such has info on the 400's. I've just about wrapped up the 416, and it's pretty quiet, so I have nothing to suggest. I'm sure you have already oiled everything that could take oil.
This is far fetched....could the feed dogs be banging into the needle plate?
Does it make the noise with and without the bobbin case?
Last edited by k9dancer; 12-02-2012 at 04:39 PM.