We may have found other answers which could help you.
Click here for Timing Sewing Machine
the thread is bunching on underside of fabric it looks like birdnest?
Singer zigzag 457 Stylist not threading bobbin/making stitch?
What size needles can I use for my Singer 39a3?
Bobbin won't wind?
Need a service manual for a Singer Treadle Sewing Machine Model 66-1?
Singer 507?