We may have found other answers which could help you.
Click here for Sewing Machine SewToyota SL3404D Overlocker leaving big loops?
Sewing machine issue?
Sewing machine starts on its own?
How do fill a bobber?
Sew-tric ltd variable speed motor built 1982 6000rpm r007327?
Singer zigzag 457 Stylist not threading bobbin/making stitch?