I had a very interesting case with a 25-PDVC that had a top auger jam. As an experiment, I cleaned out the top auger, buffed it down with a wire wheel and sprayed it with dry moly. Then I installed a high quality ball bearing auger motor and fired it up without touching the bottom auger. The top auger still jammed up! So then I pulled out the bottom auger and to my surprise it was black as night with carbon! The worst I had ever seen! So I buffed it all clean with the wire wheel and sprayed it down with dry moly. Then I re-installed it and it has been running good for over a year now!. A big lesson learned. Both augers should be clean as a whistle!