What Causes A Riding Lawn Mower To Cut Uneven?

An investment in a riding lawn mower is no small affair, so it makes sense that anything less than a pristinely cut lawn is unacceptable.  As such, when you look back on your handiwork and notice that your lawn is unevenly cut, it makes sense that you might wonder aloud, “What causes a riding lawn mower to cut uneven?” 

The chances are pretty good that the solution is a simple fix once you have identified the problem.  Let’s look at some of these issues and find out which cause might be mechanical, and which might result from human error.

Could It Be Blade Issue?

What Causes A Riding Lawn Mower To Cut Uneven

The heart of any lawnmower that determines cutting performance can be found in the machine’s blades.  If the blades are not operating precisely, you will never achieve that even golf-green look in your yard.  Indeed, if you are suffering from an uneven cutting, there is a myriad of reasons why your blades may be the culprit. One could be the crankshaft, you can view lawn mower bent crankshaft symptoms here.

Moreover, if it is your blades are causing the problem, you are only halfway to your goal of discovering what aspect of the blade is causing the problem.

Blade Synchronization

For your ride on mower to cut correctly it is necessary for the blades to operate correctly in parallel.  What this means in practice is that the blades must be cutting the same length sideways, which is designed to cover the maximum range possible.

If you notice that the blades are not synchronized simply realign them correctly to ensure that you are reaching the maximum potential of each blade.  If, after making this adjustment you notice that it has not solved the issue, consider removing them before fully reinstalling your blades.

Dull Blades

An obvious problem, dull blades will result in an uneven cutting pattern and uneven grass.  If you note that your ride on mower’s blades is dull the simple solution is to sharpen them. 

Consult your owner’s manual for the correct steps to sharpen the blades safely.  While they sell sharpeners and balancers for the DIY’ers, as with most things that can potentially be dangerous, it might be equally easy to find a professional to handle the job for you.  Generally speaking, the cost to sharpen the blades should be $10 to $15 or so.

Best Lawn Mower Blade Sharpening Kit:

Damaged Blades

We ask a lot of our ride on mowers, so it probably should not be a surprise when the blades get damaged.  Stumps, rocks, logs, and more are all potential causes of blade damage, and the damage will be evident upon inspection.  Nicks and breaks in the blade will absolutely cause your ride on mower to cut your grass unevenly, but luckily the repair is a simple one: replace the damaged blade.  Consult your owner’s manual for the model number of the blade to ensure you get the correct one.

Best Riding Lawn Mower Replacement Blades:

Worn Deck Pulleys and Blade Belts

As with all machinery, elements break down and become worn over time and your ride on mower is no different.  Your blades are driven by the array of deck pullies and blade belts, and when they start to fail you will notice an array of issues effecting your machine’s performance including an uneven cutting job on your lawn.    

If an inspection reveals worn or frayed belts that could well be your problem.  A worn deck pully will force the blade to vibrate, while a worn blade belt will not spin the blades properly, and either will result in an uneven cutting of your grass.  The permanent solution Is to replace all worn and frayed deck belts and failing deck pully systems.

Spindle Issues

At that point where the blades of your ride on mower mount to the housing assembly containing the bearings, known as the spindle, can malfunction, which will result in an irregular and uneven cut.  Generally, if the spindle becomes loose or bent you will need to either attempt a repair or replace the entire unit.

To repair or replace a faulty spindle assembly begin by removing the deck and attendant deck pullies and blade belts.  When moving to remove the spindle assembly, use penetrating oil to remove the bolts, let it soak a bit before attempting removal. 

Once removed, you will need to disassemble the unit to get at the bearings.  There should be a part number imprinted along the spindle, which you should write down because you will need this information to order a new replacement part.    

What Causes A Riding Lawn Mower To Cut Uneven: Could It Be a Deck Issue?

Your ride on mower comes equipped with a deck that is designed to prevent debris, such as sticks and stones, from flying upwards potentially causing potential personal or property damage.  Additionally, the deck channels grass clipping off to a single side that allows for an easier time during the raking and cleanup portion of your yardwork.

Mower Deck Level

To achieve an optimal cutting job on your lawn, your ride on mower deck must be set at specific height that the manufacturer has kindly noted as the recommended setting.  Alas, oftentimes we forget to set the recommended height, or more likely the bumps and knocks of operation and rendered those settings moot.  

Consulting your owner’s manual will provide specific information on how to level your deck and will note the actual height difference between front and back.  Armed with this information, you then measure your front and back deck heights before adjusting to hit that perfect sweet spot.

Best Riding Lawnmower Deck Leveler:

Faulty Mower Deck

As mentioned above, your deck serves to block flying debris while channeling your grass cuttings to one side, but if you are suffering from a busted or faulty deck, all the leveling in the world will not result in a neat golf course-style manicure.  If, following inspection you find your deck to be faulty, your options are two-fold including repairing it replacing it.  Depending on the level of damage, you might get away with bending or pounding the deck into proper position, or deeper problems might need the attention of your friend with welding skills.

Clogged Deck

Of the potential deck related causes of an uneven lawn mowing, a clogged deck is the easiest to fix by far.  Grass, dirt clumps, and debris accumulates over time, and can influence the action of the blade, will potentially result in an uneven grass cutting.  Simply check for obstructions and clean them out before trying again.

Best Lawnmower Deck Cleaning Tool:

Tire Pressure Can be an Issue?

Perhaps one of the nicest features of a modern ride on mower is its ability to travel just about everywhere it needs to go that needs cutting. 

Part of this abilities owes to its tractor-style tires, which can crawl over the beefiest obstacle, albeit at a definite detriment to the condition of your deck as mentioned above. 

That said however, if you are experiencing an issue whereby you are getting an uneven cut, you may want to check your ride on mower’s tire pressure.  An improperly inflated tire can yield a host of problems from mower wobbling to weird steering, and yes, even an uneven cut. 

That is because this condition will cause your deck to sit unevenly thus resulting in poor cutting performance.  As a rule, factory settings for your residential-use ride on mower is 14 PSI for the front tires, and 14 PSI for the rear.

The Problems with Humans

This may prove an uncomfortable portion of the conversation, but at this point, baring any of the above coming into play, is the fact that your uneven cutting issue might be put down to human error.

I know.  I know.

That being said however, they may be a few stylistic moves that you are making while “cutting that back 40,” which is affecting the quality of your lawn cutting job.  Specifically, two operator factors might lead to uneven cutting results.

Mowing Too Fast

While it is understandable that you might want to get out of the sun and enjoy a cool beverage in the shade, moving too fast can be a cause of that uneven cut that you are shaking your fist towards.  While the obvious solution to this problem is to slow your roll, the reality is a bit more complicated.  Indeed, you will wish to play around with your ride on mower’s settings while checking out the cut at varying speeds.  Keep in mind, riding too slow can also cause problems, so always mow at full throttle and be on the lookout for that sweet cutting spot.

Incorrect Turns and the Failure to Overlap

You are more likely to end up with taller grass when you fail to overlap your route correctly.  Noting your turns, you mighty determine that your turns are overly sharp and leading to an uneven cut.   Make sure hat you are making slow, fulsome turns and take the time to line up each pass so as to ensure the proper overlap.

Find the Technical Support You Need

Whether you consider yardwork therapeutic or a chore, doing the job on the back of a ride on mower makes the entire experience easier.  When it comes time for troubleshooting problems in the yard however, your owner’s manual and the internet are excellent sources of information for your specific make and model of ride on lawn mower. 

Keep in mind however, whenever you are looking for replacement parts for your machine, you will need to locate two numbers: model and serial numbers.  Conversely, should you be looking for a new motor part, you will need to identify the specific model and serial numbers for the engine, which will be different from those for the machine itself.