I found that works with my Janome. Also, holding the thread up top really tight until bobbin is partially wound, then clipping it. I was initially frustrated by the bobbin winder and bought a Sidewinder that was lousy.
I loop around the back guide a couple of times to make sure the tension is tight.
Originally Posted by sewing4kix
I have a Janome 6600P and was told by my repairman that I needed to wind my thread around the round feeder on the top of my machine 2x before adding the bobbin for winding. He told me that the extra tension it provided would make a tighter wound bobbin and that would prevent it from unwinding and causing a tangled mess underneath. Hope this helps you out.