So you have a new John Deere riding mower, and you’re just itching to get out there in the yard, put your earbuds in, and turn your lawn’s wilderness aesthetic into a disciplined, smooth lawn. Once finished, you realize your yard looks like a Super Mario Bros. platformer instead.
While uneven cutting is unfortunate, it’s usually a fixable problem. For example, you may have a bent mower blade, uneven tire pressure, a clogged mower deck, slow engine speed, you’re moving too fast, or you’re dealing with a damaged spindle or spindle housing.
There are more potential scenarios here, but we prefer to go over the most common issues first and foremost. Unless you don’t really have a new John Deere or you just purchased one used, you should only run into these problems occasionally, while making an adjustment will set you right as rain.
Reasons Your John Deere Mower Is Mowing Uneven
So let’s take a closer look at the different issues you can run into and how to solve them below.
#1 Your Tire Pressure is Off
It might surprise you that it may be a simple fix, such as having lower air pressure on one side over the other. But, unfortunately, it’s often hard to tell, especially if your John Deere is sitting on soft earth or you’re trying to mow down the jungle that your yard has become.
All John Deere riding mowers—all John Deere machines, period—come with user manuals that tell you the exact amount of pressure you should have in each tire for optimal performance.
Checking your tire pressure and maintaining your tires is the first thing you should check over if your lawn is cutting unevenly, especially if the uneven cut is only a little off.
#2 Bent Mower Blade
Have you ever been riding along, cutting your grass, when a horrible, ripping, exploding sound emanates from below the mower deck, and your engine bogs down under stress?
We’ve all done it—hit that annoying log that should have been sticking out like a sore thumb but was buried deep in the grass you’ve been neglecting for weeks.
Most of the time, you will be okay or, rather, your John Deere will be okay. However, that’s not always the case, or you wouldn’t be reading this article right now.
By looking at it, you’ll know it’s bent for sure, but your lawn will look terrible too, even if the bend in the blade is only slight.
To avoid a bent blade, always run some reconnaissance on your back yard first, walking through and checking that no branches fell in the night and that none of the trees have roots sticking up too far for your current blade level.
Before you check below your mower deck, place the John Deere in the park position and make sure you are on a flat surface. Then, you can either remove the blade entirely or run a few measurements from the ground to the tip of the blade and another from the ground to the inside of the blade.
If it’s bent, you will have to replace it before it can do any additional damage to your land or your John Deere.
#3 Clogged Mower Deck
Grass can quickly build up underneath your mower deck and will go unnoticed until your John Deere is no longer mowing the lawn evenly throughout. The blades work by creating suction as they cut, which forces your grass blades to stand tall and take what’s coming to them.
When you have far too much grass underneath your mower deck, the suction process can become a bit disabled.
When this happens, your grass will not stand up, at least not as well. Often, only portions of the grass may stand up from the weakened suction, resulting in an uneven cut.
The solution is to access the underside of your mower deck. It’s not a pleasant job but a simple one at the end of the day.
#4 Slow or Fast Engine Speed
This is where things could get more complicated, depending on what is causing your engine to run slower or at lower RPMs than it is supposed to. Most of the time, this will only happen when you are not running your John Deere at full throttle.
Sometimes, you may accidentally bump the throttle lower when you don’t intend to, so it’s worth keeping an eye on. If it has nothing to do with the throttle, then it’s time to take it to a mechanic and see what is happening.
On the flip side, running too fast will present an uneven cut. Also, the RPMs will rev up much higher when cutting through heavy grass, so you need to adjust the throttle on the fly.
#5 Damaged Spindle or Damaged Spindle Housing
The spindle and the housing that holds it are designed to keep your blades level, no matter how complex or straightforward the cut is.
Fortunately, the spindle is an easy one to figure out.
All you need to do is reach down and grab the very end of the blade (make sure your lawn mower is off and the key is not in the ignition, or it may be the last thing you ever grab ahold of) and rock the blade up and down.
It’s easy to feel if the spindle doesn’t secure the blade because the rocking up and down motion will be erratic and slip a lot.
Unfortunately, if it is loose, it will require you to completely remove the blades and probably replace a bearing in the spindle as well.
This is either something that you should leave to a mechanic or something that will take a little while to complete as a DIY project. You want to look for a bad bearing once you have everything fully disassembled.
John Deere sells bearings, but, depending on the model John Deere Lawnmower you own, the bearing may be something that has to come with its own spindle, meaning you will have to replace the entire spindle even if the only thing that’s bad on it is the bearing.
#6 Bad Deck Belt or Pulleys
Your belt and pulleys are responsible for spinning the blade. How fast the blades spin is how well your grass will cut. You can only check the status of your belts through direct observation.
Always check for cracks, even if your belt is cupped too deeply into the well of the pulley. You should be able to pull the belt and spin the blades. However, if you experience resistance, you must change the pulley and belt out.
If you are getting a grating or squealing noise from the pulley, you should replace all of it, bearing assembly and pulley. Fortunately, this isn’t too difficult a job. So long as you have pretty nimble fingers, you can quickly swap out the belt, pulley, and bearing.
#7 Dull Mower Blades
We saved the easiest for last or, at least, the easiest to diagnose.
It’s natural for your blades to dull over time, and you can use a good file to sharpen them. You’ll need to remove them to work on the edges. If you don’t feel comfortable removing or filing the blades, you can take the machine to a mechanic.
Dull blades are the opposite of what you need for an evenly cut lawn. However, you will get an even cut every time with sharp blades and a smooth running system.
All lawn mowers will experience issues that can cause uneven cuts, even a reputable product like John Deere. The best way to ensure it cuts properly and avoid problems is to service your machine regularly and to keep an eye on the blades, ensuring they are always sharp.
If you experience issues with uneven cuts, John Deere has an excellent customer service line that will help you figure out what is going wrong and how to fix it.
You can take it to your local John Deere dealer, and they will be more than happy to help you out.