This may cut your ultimate capacity but the way you clean the sample up is:

Set the sieve (lower) as close as possible without running too much clean grain in the return (tailings) elevator which is easily checked on the go beneath your seat (wish the new combine could do that). When setting it close be aware that if you start pushing cqapacity clean grain will overload the sieve and the return will quite rapidly overload. There is a fine line between close and too close when you are trying to clean dirty grain up. Leave the cab inspection door open for a while while you are adjusting settings (not the return elevator door - get the cab really dusty, just open it when you wnat to look) and you can hear the grain in the return elevator in corn or beans if the amount becomes excessive.

Set chaffer closer than normal, probably 1/2 to 2/3 book setting. Basically set it close as possible without overloading the chaffer and throwing grain out the back. This will reduce maximum capacity but also reduces the amount going over the chaffer so the sieve can be set closer. Book setting for air will probably be ok but you can play with it up and down a little - too much and grain/mog layer will exit combine too fast and not give time for grain to drop through (blow grain out the back). Too little air and grain/mog will suddenly loose suspension and drop onto the chaffer and grain will ride out the back big time.

Try not to over-thresh. Only use enough cylinder speed and concave clearance to get the grain out. Any excess will grind up the green plant material and make more green stuff for the cleaning system to seperate. If the grain is tough or green this may be the opposite for what you need to get the grain out of the head.

You will probably have to live with some green in the grain. The combine uses differences in weight and size to do the seperation process. If the green material pieces mimic the size and weight of the grain the system has no other way to distinguish it from grain.

Good luck and have fun. John Deere alsays had great cutaway pictures of combines in their sales brochures showing the operation of the combine and they also published "Fundamentals of Machine Operation" manuals that were used in a lot of Ag classrooms and could be purchased (I have a complete set that is about 20 years old). If you can get your hands on some of this information and study the way the combine works adjustments will be a lot easier and make more sense.

John