Maintaining and properly adjusting your combine are important steps to consider before harvest. These activities will maximize your harvestable yield and grain sample quality during harvest. The following considerations will help you focus on the most important steps to help maximize combine efficiency.

Combine maintenance must occur pre-season and during the season to maximize grain quality and limit harvest losses without incurring downtime. Here is a short maintenance checklist that is not brand or model-specific.

Start at the front with the feeder house.

 Ensure the chain is properly adjusted, and the slats are running squarely. If they’re not, one side might have jumped a sprocket tooth. If this chain is running loose, it will create added power consumption and provide poor feeding into the rotor. Check the feeder house floor for thickness, as it will wear over time.

Check all belts for cracks, splits, and hot spots.

 If any are found, make sure to replace them. Some belts, like the feeder house drive belt, require a high amount of side load, so pay special attention to them.
Check all chains and sprockets for wear.

Run the machine with the thresher turned on.

 After running for a period, use a temperature gun to check every bearing. If any bearings are hotter than the rest, it would be a good time to change that bearing before failure occurs.

Check the concaves for rounded edges, missing wires, and cracks.

Evaluate the threshing elements on the rotor and the rotor cone itself for thickness.

 While looking at the rotor, inspect the vanes at the rear of the concaves and the separation arms at the tail of the rotor.

Check all chopper knives and replace them as needed.

Adjust the clean grain and tailings conveyors.

 Having these set correctly will help to prevent damaged grain.

Check all augers for thickness and sharp edges and replace them as needed.

 Ultimately, you want to ensure that these devices will spread the width of the header.

Inspect the chaffer and shoe frames/mounting points/arms for cracks and wear.

Inspect the chaffer and shoe for missing or bent fingers and replace them as necessary.

Look over all gearboxes for smooth operation and oil quality.

Check stalk rolls and deck plates for wear and alignment.

Set the header angle correctly. This value should be found in the header manual.

Even with hydraulic deck plates, it’s still critical to adjust the fixed deck plate for an initial measurement. You can do this by utilizing a socket to slide between the plates. They need to be a little wider at the back of the plate than at the front. You can find this value in the header operator’s manual.

Adjust the auger height relative to the floor. This will limit broken ears entering the machine.

Check all guards and sickle sections for sharpness. Replace them as needed.

Inspect draper and drive belts, sprockets, and chains for wear.

Inspect floor pans and shoes for thickness.

Look over reel fingers, bushings, and overall operation.

Ensure the head angle is correct per the operator manual.

Refer to your owner’s manual for a complete list of the settings for the make and model. of the machine that you have.

Prepare your yield monitor for harvest by uploading previous maps to your preferred record-keeping software.

Calibrate the yield monitor and moisture sensor in relation to a certified scale and moisture sensor.

There are two types of loss created by the combine: pre-harvest and mechanical loss.

Pre-harvest loss can be caused by wildlife, weather-related events, or the natural dry-down of the crop being harvested.

 Usually, these losses are out of the grower’s control.

Mechanical loss is created by the header or the combine itself.

 Most of these losses are in your control and can be minimized by performing the maintenance steps from above or by fine-tuning the combine settings.

To determine if the loss is pre-harvest, header, or machine, follow this list:

Walk the field to check for dropped ears, kernels, or soybean pods/seeds. Take these counts into consideration for the next step.

Each dropped ear in 100 plants equates to a 1% loss

In soybeans, 4 seeds /Ft2 equals 1 Bu./A.

Once you have determined the pre-harvest loss, the mechanical loss can be determined by harvesting the field. Don’t forget to record these numbers.

Step 3: Determining Where Mechanical Loss Is Coming From

Machine loss can be divided into three separate categories:

 header loss (associated with kernel/seed loss at the head), threshing loss (grain left in the pod or kernels attached to the cob), and separating loss (which is when the seed/kernel is blown out the back of the combine).

 Start harvesting at the average speed for several hundred feet, then stop the machine to evaluate:

: Lift the head and install the stops. The area from under the header to the middle of the combine will be header loss. Use a 1 Ft2 tool to calculate this loss. Take a couple of counts to get a good average, and look for ears that did not make it into the header. Record these values.

: Threshing losses would be found at the back of the machine. Try to check for losses on the standing crop side of the pass. Corn left on the cob or unthreshed soybean pods on the ground would be a sign of threshing loss. Another form of threshing loss is cracked kernels or split seeds in the grain tank. Take a sample to check for these and record this value.

: Utilize the same area that was used for threshing loss; check for kernels or soybean seeds left on the ground. Utilize the 1 Ft.2 tool to calculate and record this loss.

 Take the values found from header, threshing, and separator losses and add them up.

Header + Threshing + Separator – Pre-Harvest = Total Machine Loss

The industry standard is a 3% loss (6 kernels of corn and 12 soybeans per square foot).


If losses are less than 3%, then no adjustment is warranted at the time. Remember, crop conditions can change rapidly from field to field and throughout the day, so small adjustments will more than likely be necessary. If the total machine loss is over 3%, then adjustments should be made.

Step 4: Machine Adjustments To Limit Grain Loss

Below are adjustments you can make to limit mechanical losses. Remember to start at the baseline settings in the manual or harvest efficiency guide for your machine.

: If kernel loss is found at the head, start by setting the deck plates narrower and double-checking the header angle. If ears are found, start by adjusting the ground speed, gathering chain speed, or adjusting the orientation of the gathering chains.

: If high losses are found from the platform, there are a few things that can be adjusted.

If pods are shattered from the reel, it is justified to slow down the reel or raise it.

If the grain is falling from the cutter bar, increase the ground speed or reel speed or lower the reel height.

If the crop is lying on the cutter bar, lower the reel and/or move it rearward.

: In most situations, adjusting the concave should be the first adjustment. The rotor speed can be changed for fine-tuning. In the case that some pods are tough to thresh or you’re leaving quite a few kernels on the cob, it is best to tighten your concave first instead of speeding up the rotor. If you have minimal threshing loss but want to get it better, it’s acceptable to adjust your rotor speed first. If you are getting cracked kernels, split soybeans, or excessive cob in the tank, you should loosen the concave, then slow down the rotor for fine-tuning. It is a good practice to utilize the lowest possible rotor speed that will still thresh the grain but avoid unnecessary breakage.

: If the amount of separator loss is unacceptable, the first thing you should do is increase the fan speed. Grain is more than likely riding out the back of the combine with the other plant material. By increasing the fan speed, you can lift the plant material up and allow the grain to fall through the sieves. If you’re still experiencing too much loss, adjusting the chaffer sieve to a wider opening should help catch the grain with the sieve fingers. The only time the bottom shoe sieve adjustments should be made is when changing crops or when too much trash is present in the grain sample/overloading of the tailing’s auger.

Step 5: Final Steps For A Successful Harvest

Losses cannot be completely reduced, but it’s critical to keep losses at or below the industry standard of 3%.

Carry a notebook in the cab as you adjust settings and record them in relation to loss and grain sample quality.

When recording, record the date, harvest moisture, and crop. 

You can then use these values when switching crops or in following years as a baseline.

Header efficiency is the most important factor in maximizing capacity without loss.

 The largest percentage of loss comes from an improperly adjusted head.

Operate the machine at full throttle and keep an even, uniform flow of material through the combine while harvesting.

 Make sure to operate at a ground speed that doesn’t overload the machine, and ensure your rotor speed and concave clearance are set at the correct setting for the crop.

When it comes to the sieves, make sure they are open enough to allow the grain to flow through.

 If they are too open, sieve overloading and a poor sample can result. If they are set too tight, grain can flow over the top and plug the tailings elevator.

The last thing to check is that you chose an appropriate fan setting.

 If it’s running too fast, it can cause crop loss. If it runs too slow, it can cause sieve overload. Remember, there is a balance between foreign matter in the grain tank, grain quality, and loss.

Ultimately patience and checking for loss is often critical throughout the harvest season.