what could cause black specks to build up in my embroidery sewing machine?

I have a Brother Super Galaxie 2000 (sold as 8200 in US I think) that is building up black, carbon like material around the needle arm area and throwing black specks all through the machine and onto the sewing project/area. I have had it to the service guy half a dozen times (I think) and he has set the timing, bobbin tension, replaced the support arm for the needle bar, replaced the needle bar, the main "cog" and made adjustments over the course of these trips. (He has not been charging me for these, and I dont believe he is trying to rip me off, I just think it is beyond him and there is no one else in the area).
I have thoroughly cleaned the machine, he has taken it apart and cleaned it, and I am just about at my wits end with this. Does anyone have any idea or has anyone experienced something similar?