What causes a riding lawn mower to cut uneven

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The surest way of solving the issue of your riding mower leaving taller/shorter grass in some areas is to first understand what causes a riding lawn mower to cut uneven.

The good news is that some of the issues behind uneven cutting are quite basic and you can eliminate them without involving an expert.

Read on to learn why your mower is cutting unevenly (step-cutting) and how to troubleshoot your riding machine’s awful cutting.

riding lawn mower not cutting evenly

What causes a riding lawn mower to cut uneven- basic issues

As I mentioned, it’s sometimes a very minor issue so it’s important that you first check the basics.

You might be surprised to find that your cutting woes are caused by something simple like tire pressure (more on this shortly).

Here are the most basic issues and possible workarounds:

1. Tire pressure

Under-inflating or over-inflating the tires can bring up plenty of wrongs including weird steering, mower wobbling, and making the deck to sit unevenly.

It’s the latter that is more worrying in this case since it inevitably results in uneven cutting.

What to do:

You must check the tire pressure and see to it that you have inflated the 4 tires to the manufacturers’ recommendation- sorry, but there are no two ways about it.

2. Mower deck level

Another primary cause of uneven cuts is an unleveled deck.

You see, your riding lawn mower deck must maintain a certain cutting height to achieve a well-manicured lawn after each mowing.

But, of course, we are humans and can forget to fix the recommended setting.

Not only that:

The deck height might have misadjusted after hitting bumps and debris.

Lastly, you may also have unknowingly disturbed the deck level when changing blades, if you have done that in the recent past.

What to do:

Measure the heights of both the mower’s front and the rear blade tips to the ground.

You then refer to the operator’s manual for accurate height differences between the front and rear and raise/lower the deck to the sweet spot.

The manual should again have the specific instructions on how to level the deck for your model.


Watch this video for the exact procedure if you own an MTD/Troy-Bilt Riding Mower.

3.                     Clogged deck

Grass and debris build up under the deck over time, especially when it’s wet and it may be to blame for the uneven cutting.

What to do:

Clean the grass clippings from the deck and retry.

What causes a riding lawn mower to cut uneven- operational reasons

The basics help but the mower won’t cut crisply without solving all other issues hampering it including an incorrect operation.

In this section, we shall concentrate on the causes related to how you operate the mower.

Let’s begin.

4.  Mowing too fast

Could it that you are going too fast?

Well, for the most part, mowing rapidly can cause those unsightly stripes.

I know that we all want to save time – and it’s perhaps the reason why you went for a riding mower- but extreme speed hurts even cutting.

What to do:

The answer here is obvious: slow down and observe the cuts at different speeds.

Even so, don’t ride exceedingly slow as that can also produce uneven cuts.

In addition, the engine should be mowing at full throttle- you only slow your ground speed.

5. Failing to overlap cuts or turning incorrectly

The mower will leave tall/lower grass if you don’t overlap the cutting row adequately or you’re making very sharp turns.

What to do:

The only solution here is for you to overlap cuts enough or make wide turns to allow it to reach every blade of grass.

What causes a riding lawn mower to cut uneven- blade issues

You guessed it right- if the blades aren’t in perfect condition, it will never cut clean.

Here are the myriad possibilities surrounding the blades and how to approach each:

Reason 1: Blade synchronization

If the blades are not in parallel, they won’t catch the grass that falls within the maximum clearance area between them very well causing unevenness/missed areas.

What to do:

Inspect the blades to ascertain if they are synchronized (in parallel) with each other. This simply involves observing if they’re cutting the same length “sideways”.

If not, position them such that they are aligned evenly in a straight line to cut the maximum range.

If the problem perpetuates, consider removing and fully reinstalling the lawnmower blades.

Reason 2: Dull blades

Blunt blades are another pretty straightforward reason.

What to do:

Follow the steps illustrated in your operator’s manual to sharpen the blades.

Reason 3: Damaged blades

Damaged blades are also a major cause of unbalanced cutting height and you will need to check if it’s worn out too far.

What to do:

This also has no shortcut – just replace the affected blades.

Reason 4: Worn blades belt/ deck pulleys

A worn blade belt can fail to spin the blades as desired as does worn deck pulleys (these can also cause the blades to vibrate).

The outcome is again the annoying uneven cut.

What to do:

To permanently fix these, replace the worn belts and failing deck pulleys.

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Riding lawn mower not cutting evenly: other causes

Modern riding mowers are quite sophisticated and could be leaving strips of unevenly cut grass due to the following reasons:

·         Spindle problems

You could be facing a spindle (the housing -with the bearing- where the blades mount to) problem.

Specifically, you will always get an irregular cut if, for whatever reason, the spindle is bent or loose.

What to do:

Try to repair, where possible or buy a whole new unit and replace it.

·         Faulty mower deck

A damaged mower deck will negate all your leveling efforts and further frustrate your efforts to bring out a world-class lawn.

What to do:

Inspect and replace the bent mower deck

Final tips

Riding lawn mowers are also known to cut unevenly because of uneven weight distribution but the above are what causes a riding lawn mower to cut uneven mainly.

It’s now upon you to go ahead and implement the various suggestions in order to have the mower cut precisely again.

Remember to take the necessary precautions before you start diagnosing the mower as specified in your owners’ manual.

Talk to your dealer or repair shop if unsure of any step and in the event that the problem persists or invest in one of the best zero turn mowers for uneven ground.

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