Originally Posted by eimay
Be sure you are using only Janome bobbins. Some bobbins on the market say they can be used in the Janome. They can't. Janome's bobbin works off a "floating magnet". The "universal" bobbins can be off just a smidge, but cause problems. Also if you do not have your thread firmly in the take up eye, you may have a problem. Also be sure your bobbin is in the correct direction (The thread should form the letter P before you put it in). Hope this helps.
I have a Janome 6600 and was experiencing the same thing with the bobbin rattling, sometimes causing a nice little birds nest to form on the back. Before freaking out, I decided to try using only Janome bobbins, and it worked like a charm. I clean the lint out regularly, definitely between each bobbin change. It's like liposuction, only easier.