Corn Head and Combine Adjustments: Getting Ready for Harvest

Before taking your combine into the cornfield, a little preseason prep can go a long way toward maximizing performance and protecting grain quality. Today, we’ll walk through the key adjustments to make on your John Deere corn head and combine before harvest. This applies to the C12F, 700 series, and 600 series heads, as well as S-Series machines.

Inspecting the Row Units

Row units are the first point of contact with the crop, so they deserve careful inspection. Gathering chains should be tight and fingers in good shape to grab stalks and pull material smoothly. If fodder builds up at the front, adjustments can help: swapping the chains so they run “backwards” creates a more aggressive pull, while timing the tines together provides the most aggressive setting for dry conditions.

Remove the chains to check sprockets and roller bearings, both upper and lower, for wear. Stripper plates should be free-moving with no half-moon wear patterns. They need to adjust easily to different stalk diameters to minimize butt shelling. Rolls should be inspected for cupping and alignment to ensure they’re breaking stalks properly.

John Deere offers three roll options: opposed rolls, intermeshing rolls, and RowMax chopping rolls. The opposed style is the traditional design but struggles in dry fodder, while intermeshing rolls provide a strong crimp and pull plants through effectively. The RowMax chopping rolls are the most aggressive, cutting stalks into fine material that breaks down quickly and stays close to the root ball for better residue management.

Gearboxes and Lubrication

Each row unit gearbox runs in an oil bath. Check levels with the dipstick and ensure oil sits between the marks. Use 80W-90 GL-5 gear oil, and replace it every 200 hours. The drive chain oil bath, located on each side of the head, should also be checked and replaced every 200 hours.

Slip clutches only require about 10 pumps of polyurea grease once per season. Over-greasing can cause slipping, so less is more here.

Auger Levelness and Feeding

Feeding efficiency depends heavily on auger setup. On folding corn heads especially, check the auger levelness across the table. All augers should sit evenly to prevent uneven feeding and reduce kernel damage from cobs lodging under the flighting.

Drive chains for the augers also need attention, inspect links closely for wear or cracks, adjust tension properly, and replace chains that look suspect before heading to the field.

Sensors and Precision Features

Modern Deere heads may include RowSense and header height sensors. For RowSense feelers, maintain a gap of 1.5 to 2 inches; too wide and the system may revert to AB line guidance, reducing steering performance.

Header height sensors, located at the ends and center, should be checked for intact springs and functional potentiometers. Clean connectors thoroughly, as dirt and debris can disrupt readings. Follow wiring harnesses to check pinch points where damage often occurs.

Active End Fenders and Stalk Deflectors

C12 and C8 models feature active end fenders, which help gather ears in down or tall corn. Inspect roller bearings and hydraulic hoses for buildup or wear. Ensuring doors open freely, raising them helps keep ears in the head when cutting tall corn.

Stalk deflectors, available since the 700 series, mount beneath the rows and are designed to lay, break, and crush stalks for quicker breakdown. Their aggressiveness is adjustable, but be cautious: if set too aggressively, especially in damp fodder, they can ball up material and cause clutch slippage.

Greasing and Maintenance Points

Daily grease points include folding hinge points. PTO drive shafts require greasing every 50 hours, and slip clutches every 200 hours (or once per season). Keeping up with these intervals helps avoid in-field downtime.

Rotor and Concaves

Think of the rotor as two zones: the front handles threshing, while the rear is for separating. Round bar concaves are a solid choice for corn, but Deere’s Condex concaves offer versatility for both corn and soybeans. In tough, high-moisture corn, inserting a wheat concave in the first position can provide extra aggressiveness to strip kernels off the cob.

Leveling is critical. Close the concaves fully and measure front and back to confirm even spacing. An uneven concave often causes cleaning capacity issues. A quick field method for setting clearance is to use an actual cob, adjust until a bare cob just passes between the rasp bar and cage, then fine-tune based on hybrid differences.

Inspect rasp bars and separator tines for wear, replacing them in sets of three to maintain rotor balance. Separator grates come in general purpose and heavy-duty versions. The heavy-duty style adds fins that disrupt crop flow, allowing more grain to fall through, useful for high-yield or tough corn. If you’re running standard grates, alternating spacers can simulate the same effect by creating “speed bumps” that help grain separate.

Chaffer and Sieve Adjustments

Broken cobs are the main issue here. Check daily for lodged pieces in the fingers, which can block movement and let trash into the grain tank.

Two styles are available: general purpose and deep tooth. The deep tooth option is recommended for corn, as it offers greater capacity and allows residue to float on a blanket of air. However, it can be less effective in soybeans, so know what setup your machine has.

Chopper and Spreader Settings

For corn, the chopper should be in slow speed with knives fully retracted, cobs can severely damage them. Deere’s spreader system handles residue well without much adjustment needed.

Elevator Systems and Sensors

Clean grain and tailings elevators are critical for throughput. Inspect chains and paddles, removing links if necessary but replacing when stretched too far. Worn paddles can bottleneck grain flow, especially in larger S780 and S790 combines.

Machines equipped with Harvest Automation cameras should have lenses cleaned thoroughly with glass cleaner, and housings cleared of debris. Augers feeding moisture sensors and cameras must also be cleaned to prevent fuse blowouts caused by lodged trash.

Feederhouse Adjustments

The feederhouse is the combine’s first chance to damage crops if misadjusted. Check feeder chains and slats for wear and tightness. For corn, run the drum in the raised position and use the smaller drive sprocket.

The feed accelerator should be set to low speed. Inspect slats, and if replacing with new serrated slats, consider knocking the sharp edge off to reduce kernel damage in waxy corn. Deere also offers a slowdown kit for sensitive hybrids.

Electrical connectors on the feederhouse deserve attention as well. Clean and protect pins with dielectric grease to avoid contact issues, especially during head changes. Multi-point connectors and locking pins should be inspected and lubricated before the season begins.

In-Cab Settings and Final Adjustments

Once mechanical adjustments are set, fine-tuning happens in the cab. Rotor speed should start at 450–500 RPM. Running too slow often increases rotor loss, as kernels aren’t being forced out properly. Cleaning fan speed can be set around 1,100–1,200 RPM and typically left alone.

Concave clearance should be set using an actual cob as reference rather than relying solely on book numbers. This ensures a practical match between crop conditions and machine settings.

Equipment Mobile Monitoring

Don’t overlook the tools built right into your technology package. John Deere Equipment Mobile gives you real-time visibility into machine performance and settings right from your phone or tablet. It’s especially valuable during harvest, when quick adjustments keep you running efficiently.

With Equipment Mobile, you can:

Monitor live machine data: rotor speed, fan speed, concave clearance, and more, without leaving the cab.

View diagnostic alerts: spot potential issues like chain wear, plugged augers, or slipping clutches before they cost you downtime.

Check calibrations: confirm that sensors, header height, and RowSense feelers are reading correctly.

Simplify recordkeeping: store settings and notes for different fields, hybrids, or conditions, making it easier to dial in next time.

Having that information at your fingertips not only saves time but also ensures you can make faster, more confident adjustments to match changing field conditions.

Final Thoughts

Preparing your corn head and combine before the season not only prevents breakdowns but also ensures better grain quality and cleaner fields. From gathering chains to rotors, sensors, and elevators, each system plays a role in harvesting efficiently. Taking the time now to inspect, grease, level, and adjust your equipment means fewer headaches once the corn is ready.