had the same problem on a 1480 with specitality rotor. finaly figured it out. set the concave at 1 to 1.5. there is just to much trash in there and it plugs up the holes in the wires. by settinng them this close, it cleans off the concaves and lets the grain fall through. have been having great results this year in 180 to 200 bu corn 18-24% have the rotor running around 300, sometimes more if it takes to much power, just kick it up to 400 or so. best grain sample i have ever had, seams like a whole different combine, and i have been fighting with this for 7 years.... and to finaly figure out there was such a simple solution.