You know I have had the same problem with several vintage machines including FWs. After cleaning and oiling the machine good - you are ready to wind a bobbin. Go ahead and start the process, but use your left hand to stop/hold (going slow on the bobbin winding) the up down motion of the needle bar with the thump screw that holds the needle in. The first time I wind a bobbin on a vintage machine I start very slow and hold the needle bar to make sure it does not move while I am winding the bobbin. That usually fixes my problems and the needle bar will not move after that first bobbin wind. If you can't stop the needle bar, you will then have to do what Joe and Miriam suggest and take the HW off to clean, but I'd try holding it steady first to see if you can fix the problem without taking the HW and washer off.
Nancy
Last edited by BoJangles; 01-06-2013 at 06:58 AM.