Mine wasn't working properly, so I cleaned out the little dust bunny wanta-bes and the normal things you do when cleaning the machine (I usually just turned off the Janome 6600P and restarted it, that usually took care of the problem. This time I investigated further.) Turned out the silver screw in the bobbin racer was almost out, not the black tension screw, the silver one. Tightened it up and it now works as good as ever.