if not using filler plates,then best advise i used to do is take a screwdriver and scrape of the junk stuck to the back side of the bars. its amazing how much of a diff. it makes. also try just turning the machine over by hand and letting dust fall of. thatis what my grandpa used to have me do on our ole 6600. hope it helps. hey not missing any knives in stawchopper are ya IJ if its out of sink that will shake the hell out of things too. hope i helped ya. mit