13 Reasons Your Kubota Lawn Mower Cuts Uneven

You expect a good cut from your Kubota lawn mower. If not, you would never have bought a Kubota mower. From my experience, Kubota lawn mowers give an excellent cut, especially when you get into the model lineup beginning with their 400 series zero turns.

A Kubota lawn mower may cut unevenly when it has low tire pressure; a bent or unbalanced blade; bad bearings in the spindle housing or pulley; a worn deck belt; or a damaged deck shell. Incorrectly operating a Kubota mower with a low engine speed or fast ground speed can also cause an uneven cut.

Whether you own a zero-turn or riding mower, there are many reasons why a mower gives an uneven cut. Keep reading and I’ll go through each reason and how to troubleshoot the problem.

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Follow all safety instructions provided in your equipment operator’s manual prior to diagnosing, repairing, or operating.Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

Reasons Your Kubota Mower Has an Uneven Cut

Kubota Mower Low Tire Pressure

When you encounter a cut issue, you may immediately assume the problem lies in your mower deck. Before you begin adjustments to your Kubota mower deck, look at your tire pressures first.

A low tire can throw off the level of your mower causing it to give you an uneven cut.

Don’t skip this step. Doing so may create more work for yourself. If you start making adjustments to your mower’s deck to level it before checking the tires, you may have to reverse your steps if you later find you have a flat tire.

Worn or Dull Kubota Lawn Mower Blade

A Kubota mower blade can become so worn that strips of uncut grass are left in your yard. This is caused by dirt and debris being sucked into the mower deck and wearing down the metal of the blade. There isn’t any way to prevent wearing. It is a normal occurrence.

Because wearing happens each time you use your mower, it is important to periodically check your blade. If the sail of your Kubota blade is thinner than the center of your blade, it must be replaced.

The sail is on the higher side of the blade. The sail creates air movement under your mower deck. This air movement and mower deck create a suction that stands your grass up tall so it is cut evenly.

In addition to checking your blade for wearing on the sail, you must inspect the blade edge. A dull edge will not cut precisely and will damage your grass by beating it up instead of cutting it.

Sharpen a dull blade if it is still in good overall condition. Replace a blade in bad condition.

Kubota Mower Blade is Bent

A slightly bent or severely bent blade can cause a bad and uneven cut. A blade can bend when you impact a hard object with your Kubota mower.

Sometimes the impact is so great you can feel the jolt and hear the grinding of metal. You clearly know something went wrong and you need to check your deck for a bent blade and other damage.

Other times, the impact isn’t as significant so you don’t even think about checking for a bent Kubota blade. When you are experiencing a bad cut, it is important to not only check your blades’ wearing condition, but you must also check for blade damage.

There are a couple of methods you can use to check for a bent mower blade. One method requires the removal of your mower blade while the other does not.

When checking for a bent blade, it’s a good time to check for spindle housing damage prior to removing a blade. For that, read the instructions in the next section.

Check for a Bent Kubota Blade by Removing the Blade

Safely gain access to the underside of your mower deck. If you have a lawn tractor, you may have to remove the mower deck. Remove the blade and place it on top of a new mower blade.

If the blades don’t match up and there are gaps, replace the mower blade.

Check for a Bent Kubota Blade Without Removing the Blade

With your Kubota parked on a flat surface, measure one side of the blade from the ground to the blade tip and record the measurement.

Next, rotate the blade 180 degrees and measure the other side of the blade from the ground to the blade tip and record the measurement. If the two measurements are greater than a 1/8” difference, you must replace your mower blade.

Never attempt to straighten your mower blade

It may be tempting to try to straighten your Kubota blade to save a little money. The metal of the blade is compromised when you straighten it making it weak. This weak area is likely to crack and cause the metal to break off your blade.

This gets extremely dangerous when your blades are rotating at very high speeds. Straightening a Kubota blade will put people, pets, and structures in the area at risk of injury or damage.

Kubota Mower Blades Are Not Balanced or Installed Correctly

Mower blades that are not correctly balanced and installed can cause your Kubota mower to cut unevenly. It’s important to follow the procedures in your Kubota’s operating manual to correctly install your blade with the correct hardware.

Before installing your mower blade, it must be balanced. What this means is the blade needs to weigh the same on one end of the blade as it does on the other.

A blade can become unbalanced by uneven wearing from normal use. It can also become unbalanced during the blade sharpening process. This happens when more metal is shaved off one side than the other.

Use a blade balancer to check the balance of your blade. It is a rather inexpensive tool that will save you from an uneven cut, vibration, and even engine damage.

When you find your blade isn’t of equal weight on each end of the blade, shave a little metal off the heavier end.

Another method to check a balanced blade is by hanging the blade on a nail that is mounted to your wall with the nail head sticking out of the wall about 3/4″ to 1″.

You will need to remove metal from the end of the blade that is hanging lower until the blade sits level.

Kubota Spindle is Damaged or the Spindle Bearing is Bad

When a component in your spindle housing is bad, there will be an extra movement where your blade will begin to wobble when turning. At high speeds, this can cause a significant vibration and cause a bad cut.

To check for spindle housing damage, grab both ends of a blade and rock them up and down. You are checking for any extra play or movement.

Listen for a knocking noise. If you feel or hear either of these, remove your spindle housing and check the spindle and bearing for wearing or damage.

Kubota Mower Deck is Plugged with Grass Clippings

You can’t avoid it. Every mower deck gets plugged with grass clippings, dirt, and other debris. When this happens, the area under the deck that is needed to create good airflow and suction is minimized.

This will give you a bad cut when there isn’t good suction to lift your grass tall for cutting.

In addition to a bad cut, the collection of dirt and grass clippings can put extra strain on your engine causing it to work harder and possibly shut down.

To avoid this, scrape your mower deck periodically. Wet grass tends to clump and clog your mower deck faster than dry grass.

Tire tracks also show mower prominently in wet grass. Avoid mowing wet grass if possible. If you must, make sure you scrape your deck following your mowing.

You can try using a silicone or Teflon spray to prevent the amount of debris that collects under the deck.

While there is nothing on the market today that will prevent all grass clippings and dirt from sticking to the underside of a Kubota deck, this product can help minimize the amount of sticking.

Kubota Mower Deck is Not Level

When your mower deck sits higher on one side of the deck than the other, you will get an uneven cut. To correct this, follow your Kubota operator’s manual to measure and make the necessary adjustment to level the deck from side-to-side.

You will also need to follow the manual to determine the correct rake and make any adjustments necessary. The rake is the pitch of the deck from front to rear. On many decks, the front of the deck sits slightly lower than the rear.

Adjustments and measurements vary depending on the model of your Kubota deck. This is the reason you must consult your manual to correct procedures.

Bad Kubota Mower Deck Belt or Pulleys

A worn or stretched belt will fail to move around your pulleys at high speeds. This can slow down the blade revolution and cause your mower to give you a bad cut.

Check your Kubota belt for signs of wearing. This includes cracking, shredding, or a shiny glazed appearance.

A belt that sits deep into the grooves of your pulleys is also a sign of a worn belt. Replace with a new Kubota belt when you find any of these conditions.

Next, move on to checking your pulleys. A good pulley should be secure, sitting flat and parallel to your Kubota deck. When the bearing in a pulley goes bad, it can cause movement in the pulley and cause your pulley to shift from side to side when your deck is engaged.

Slowly rotate your pulley by hand. Feel for any resistance and listen for a noise coming from the bearing. If you notice either of these symptoms, replace the bearing.

Sometimes you can only replace the bearings and other times you must replace the pulley assembly. This varies by model.

Running Your Kubota Mower with a Low Engine Speed

The blade tip speed affects the quality of the cut. Your Kubota lawn mower needs to be running the engine at full power to give your deck enough power to rotate your blades at high speeds. Always run your mower at full throttle when using the mower deck.

If you are running at full throttle, but your mower isn’t giving you the power you once had, bring your mower to your local Kubota dealership or small engine repair shop to be looked at.

Running Your Kubota Mower at Fast Speeds

Mowing conditions must be factored in when running your Kubota mower. Your engine will experience heavier loads when you use your Kubota to cut thick, tall, or wet grass.

When operating in these conditions, slow down so your mower is better able to handle the load and provide you with better cut quality.

Moving too fast through your lawn can cause your mower to push over grass and not allow it the time to sufficiently stand grass tall under the deck for a precise cut.

Incorrect Overlapping with Your Kubota Mower

I know what it is like to be short on time and try to space out your paths as wide as possible to reduce the number of paths you need to create to get the job done.

I also know that when I try to do this, I always find areas where I didn’t overlap my cuts enough leaving strips of uncut grass.

If your mower is new to you, it may take a few mowing to be able to gauge how much overlap you need to get a good cut.

Kubota Mower Deck Shell is Damaged

The deck shell can become damaged when you accidentally hit an obstruction like a post, tree, or building. A tweaked or damaged Kubota deck shell can cause a bad cut. You must repair your deck shell. If it can’t be repaired, you may need to replace it.

When replacing the deck shell is your only option to repair your mower deck, it is a good idea to get a price on a full mower deck replacement. Sometimes the difference in price between replacing a deck shell and replacing the full deck isn’t that significant.

This is especially true when you add the cost of labor involved in swapping deck components from one deck to a new deck shell. It’s always good to be informed and consider the cost of the repair with the age of your mower to make a good decision.

Lawn is Uneven

An uneven yard with high spots from molehills or other reasons can cause your mower to scalp those areas. Mowers work best on leveled lawns. While this may be the case, many people don’t have the luxury of having a completely flat lawn.

Sometimes a lawn roller will help even out your lawn and get rid of some high and bumpy areas. A lawn roller is a weighted roller.

When mowing areas with steep declines and ditches, a Kubota mower with a wide format deck will scalp the yard. These wide decks are unable to flex and bend with the dips in the yard.

You just end up with an uneven cut. It is best to use a small format mower in these areas like a push mower.