I have a Featherwegiht 221 and a Stradibvaro; a Singer under a different name. The latter is 50 yrs. old--bought it the first year we were married. The Featherweight I have had almost 10 yrs.
My Service Tech. guy said to use the canned air around the bobbin to keep any lint out and prevent a lint build-up. It sure works for me. He also said to oil the little groove-looking things in the bobbin are after everytime you have been sewing for about 2 hrs. or so. That also works for me and keeps my machines running great!
Mariah.