My son bought a 7240 for last season, and it's got the rotary air screen where the screen doesn’t actually turn, but has a rotary arm that has a brush and is supposed to vacuum the screen clean.
 
one particular field/hybrid that was causing us some issues, the screen was covered with so much sap that it looked like somebody covered it with cake frosting. 

took awhile even with a power washer to get it cleaned.