We may have found other answers which could help you.
Click here for Machine Motor Troubleshooting
What size needles can I use for my Singer 39a3?
Singer 507?
1965 Singer 275k sewing machine foot pedal?
Presser foot is loose?
Singer 201 went bang , smelt and now won’t work?
the thread is bunching on underside of fabric it looks like birdnest?