Here is a link to a FW website that you might find helpful.
http://singerfeatherweight221.blogsp...herweight.html
When I got my FW she was working fine but to be sure I brought it straight to my sewing repairman for a check up and make sure all was well with her. She was fine when I brought her home. I can’t remember what I was doing wrong now, but was doing something wrong and making the thread break. It was a simple fix and sorry I can't remember what it was now. Anyway, she is working fine now with no thread breaking issues :)