I have the Janome 1600 on a Grace Pro frame. When I have problems with the top thread breaking it has always been that the needle isn't in the correct position. Since the needles don't have a flat side to guide you on position, sometimes you have to play around with the needle. When looking at your machine on the frame, the needle would usually be in the 6 o'clock position. Sometimes you need to move it slightly to the 5:30 position. I use Organ sharp needles all the time and the only thread I have had problems with was the water soluble. Hope this helps.