We have a 643 cornhead and two combines, a 6600, and a 7720 Titan 2. The head was new in 1981 and it is original. We don't think we are getting too much fodder in the machines but maybe we are. The 6600 concave gets plugged, and the 7720 gets a wad of fodder between the concave and the straw walkers and slips the slip clutch. Wondering if anyone else has had this problem and fixed it with new rolls.Thanks.