Just a couple of ideas, one reason you might be having rotor losses in teh afternoon, and not in the morning is the condition of the corn crop. In the morning the stalks are tough so your stalk rolls work really well at pulling the corn stalk down through the head. As they dry out in the afternoons, they get more brittle causing your stalk rolls to become less efficient and causing more trash to go through your combine which causes the trash to carry some of the corn out the back. Ok, having said all that, I did a couple of things to help my rotor losses, make sure you have straight separator bars on the back of your rotor, I didn't have any on my rotor because it was a wheat machine. Also you might want to check with Calmer Manufacturing. They make kits to help with trash in the head. I bought some of thier smaller sprockets last year which slows your gathering chains down and gives the rollers more time to pull the stalk through. They work excellent.