We may have found other answers which could help you.
Click here for Bobbin Machine InsideToyota SL3404D Overlocker leaving big loops?
How to switch on light of sewing machine?
Frister & Rossmann cub 7?
Singer zigzag 457 Stylist not threading bobbin/making stitch?
How do fill a bobber?
How can I mend my Frister & Rossmann sewing machine?