While you wait for answers, we may have found some information which could help you.
Click here for Sewing Machine Repair SingerSinger 201 went bang , smelt and now won’t work?
the thread is bunching on underside of fabric it looks like birdnest?
Presser foot is loose?
1965 Singer 275k sewing machine foot pedal?
how to get the tension right on my machine?
Engine revving up ?