get rid of the round bar concave for wheat,,,run small wire through the whole rotor,,,we run the rotor as fast as it will go on hard to thresh wheat and wind up to 1000rpm ,,,also on hard the thresh wheat ,if we are getting white caps,we run filler plates on n1,,n5and n6,,,as 5and 6 is where the return comes out this gives more rub on the wheat,,,,maybe open your chaffer alittle more,,,might help,,,,but try one thing at a time this will tell you where you are needing changes