While you wait for answers, we may have found some information which could help you.
Click here for Sewing Machine IssueToyota SL3404D Overlocker leaving big loops?
Presser foot level, needle and thread guide have fallen out?
Singer zigzag 457 Stylist not threading bobbin/making stitch?
How do fill a bobber?
Sew-tric ltd variable speed motor built 1982 6000rpm r007327?
Sewing machine issue?