How to Use the Bobbin Winder on Industrial Single Needle Machine

[@knsinteriors1]

Thank you for a proper instruction, if I may ask you, when I purchased Juki the bobbin winder worked perfectly but as time goes by the bobbin moves like there is no tomorrow, and I did widen up a little by a flat screw driver but it does NOT help. If I widen the device too much wouldn't I damage the function for good? Should I replace something? I would really appreciated for your professional advice.

[@Linglut]

My wheel is not gripping the belt to make the bobbin move. Does it mean that I need to replace the belt?