NO offense, but if all you are getting is cobs, your problems are larger than my mother in law. You need on site help from a qualified tech person as you have something major broke or you need a different variety of corn or some water earlier in the year. If you meant to say "I have too much cob in the sample" then keep in mind that cob break up is generally greater at low cyl rpm. Set the concave at the diameter of the ave size cob, drop the front of the concave 1 or 2 marks to max, and make sure the grate is level , also make sure helicals are not WORN OUT in the transition area and the grate under the chopper and or impeller is not broke out. Make sure fan, air choke, and splitter and air ducts are to spec. After the material passes through the accel rolls anything that is the same size and weight as a kernal of corn, such as cobs and cob tips, is going in the bin. lighter material should be separated by air blowing the MOG out. Close the top screen -chaffer- and sieve down to the opening equal to the corn kernal and slowly start harvesting IF you are still getting too many cobs refer back to the first paragraph. If the sample is better keep opening the top chaffer to increase capacity to an acceptable compromise in your unusual condition.