Ok, I don't know what you all are calling the backlash spring, is that the little coil on the front of the bobbin. & when the bobbin thread breaks & I take it out the bobbin has spun until it has several loose loops of thread around it. I don't always put my thread through the coil, should I be using it? It's not spinning because I've stopped stitching, the bobbin thread is breaking & I'm using polyester thread which should be stronger than cotton. Or maybe the check (backlash) spring is the one that wraps the case, it adjusts with the screw, & the thread goes under it. oh, I'm so confused.