We may have found other answers which could help you.
Click here for Drive Hand PulleyWhat size needles can I use for my Singer 39a3?
My CG 500/550 Singer Sewing Machine's bobbin isn't working?
Singer zigzag 457 Stylist not threading bobbin/making stitch?
Presser foot is loose?
Bobbin won't wind?
the thread is bunching on underside of fabric it looks like birdnest?