It’s nice to get the mowing done and take the time to admire the freshly cut lawn. However, this time your lawn doesn’t look so nice. This could be due to an adjustment needed to the mower or a worn part.
A Simplicity lawn mower can give a bad or uneven cut when the mower has a low tire; worn, bent, or unbalanced mower blades; bad bearings in the spindle housings or pulleys; or a worn deck belt.
A plugged mower deck, an unleveled deck, a mower speed that is too fast, or a ground speed that is too slow can also result in an uneven cut with your riding mower or zero-turn.
Before working on your mower and mower deck, follow all safety instructions listed in your owner’s manual. You will need to take precautions to keep your mower in place and prevent it from starting.
This includes removing the ignition key, disconnecting the spark plug boots, and engaging the parking brake.
Things that cause a Simplicity mower’s a bad cut:
- Low tire pressure
- Worn mower blade
- Bent mower blade
- Unbalance mower blade
- Damaged spindle or bearing
- Plugged mower deck
- Unleveled deck
- Worn deck belt
- Bad pulleys
- Engine speed is too low
- Ground speed is too fast
- Incorrect mowing paths
- Damaged mower deck shell
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Follow all safety instructions provided in your equipment operator’s manual before 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 Simplicity Mower is Cutting Unevenly
1. Low Tire Pressure
The first thing you need to check when your lawn tractor or zero-turn is giving you an uneven cut is the tire pressure. When a tire is low, the mower deck will sit lower on one side over the other.
Complete this fix first. If you find a low tire after you make adjustments to the deck, you may have to reverse those adjustments after finding and correcting a tire pressure.
Use a tire pressure gauge and check your tire pressure. Add air to a low tire until the pressure is corrected. The pressures on the left side of the mower should be equal to the right side.
2. Worn or Dull Blades
Your blade tips can become so worn that a strip of grass is left between them when they turn under the mower deck.
Another part of the blade that can wear and affect the cut is the blade sail. The sail is the high side of the blade. When this happens, your blade is not able to create the air movement to create suction under the deck required for a good cut.
You can’t avoid blade wear. This is something that is going to happen under normal conditions because of exposure to dirt. The suction created under the deck draws in a lot of dirt that will wear the blade edge and sail.
Check your mower blades for wear. When the blade tips become rounded or the sail of the blade is thinner than the center of the blade, you must replace them with new Simplicity blades.
If your Simplicity blades are in good condition, but the edges are dull. Remove your blades and sharpen them.
3. Bent Mower Blade
A mower blade can become bent when it contacts a solid object. Mower blades spinning at high rates impacting an object can tweak the blade and bend it. There are a couple of ways you can check for a bent blade on and off your mower.
Before you remove a mower blade, it is a good idea to quickly check the condition of the spindle and bearing due to the impact that may have bent the blade. Refer to the section on the spindle housing below.
Check for a bent blade with the blade on your Simplicity mower
With your mower parked on a flat level surface. Measure the blade end from the ground to the blade. Record the measurement.
Rotate the blade 180 degrees and measure from the same spot on the ground to the blade end. Record the measurement.
If you find your mower blade has more than a 1/8” difference between the two measurements, your blade is bent and should not be reused.
Check for a bent blade with the blade off your Simplicity mower
For this step, have a good blade you can compare each used blade against. Place the used blade on top of your good blade and look for gaps or a bend in the blade that shouldn’t be there.
Do not reuse a blade that does not sit flat against the good blade.
Never attempt to straighten a bent mower blade. Doing so will compromise the metal making it more likely to weaken and crack.
There will be a risk of the blade breaking off at high speeds which can pose a danger to people, pets, or structures in the area.
4. Unbalanced Mower Blade
An unbalanced blade is one where one side of the blade is heavier than the other. This can happen from uneven wearing or during the sharpening process when more metal is removed from one side of the blade.
An unbalanced blade can cause your blade to wobble when it rotates under the mower deck. At very high speeds, the blade can cause spindle bearing damage. A significant vibration will be sent through your lawn mower.
Use a blade balancer. It’s a handy inexpensive tool to check the balance of your mower blade before you install it.
If you don’t have one of these tools, you can hang your blade on a nail in the wall. Shave metal off the heavy side of the blade until it remains level on the nail.
5. Damaged Spindle or Bad Spindle Bearing
A damaged spindle or bad bearing can cause movement in your blade when it rotates under the deck. This can cause a significant vibration and an uneven cut.
With your mower blade installed, grab each end of the blade. Rock it up and down to check for any movement or knocking sound.
When you feel movement or hear this sound, your bearing is most likely bad. Remove your mower blade and spindle housing to check for bearing or spindle damage. Replace any damaged parts.
6. Plugged Mower Deck
Mowers use the air movement created by the blades along with the deck shell and baffles to create a suction to lift your grass and allow the blade to make a precise even cut.
A plugged deck full of debris, dirt, and grass clippings reduces the area available to create good airflow and suction.
Not only will this cause your mower to give an uneven cut, but it will also cause your Simplicity engine to work harder to turn the blade through the debris. Keep your mower deck clean and free of debris.
Scrape the deck regularly to prevent excessive buildup. To minimize buildup under the deck, avoid mowing in wet conditions. Wet grass will clump and stick to your deck.
7. Mower Deck is Not Level
A deck that is not level can give you an uneven cut. When one side of your deck sits lower than the other, the mower may give you a stair-step kind of cut.
Because adjustment procedures for leveling your mower deck vary by model, refer to your operator’s manual for leveling procedures.
Makes sure your deck is level from side-to-side and front-to-rear. Note: on most deck models, the front of the deck sits slightly lower than the rear. Again, refer to your owner’s manual for the exact specifications for your Simplicity lawn mower deck.
8. Bad Deck Belt
A worn belt will fail to grip your pulleys and rotate your mower blades at the high speeds required for a good cut.
Replace the belt if the belt is stretched and no longer sits tight to the pulleys; it sits deep in the pulleys; or it has cracks or a shiny glazed appearance.
9. Bad Pulleys
The bearings in the pulleys on the mower can become bad. This can cause your pulleys to not sit flat and secure to the deck.
There may be some vertical movement in the pulley causing one side of the pulley to sit higher off the deck than the other side. The pulley may seize and no longer turn the blade.
To check for a bad pulley bearing, slowly spin each pulley by hand. Feel for a restriction and listen for bearing noise. When you experience either of these symptoms or a wobbling, replace your pulley.
10. Engine Speed is Too Low
When you engage your mower deck, you must have your Simplicity lawn mower running at full throttle. You need the engine speed to be at its highest to be able to send enough power to the mower deck to spin your blades and give your lawn a good cut.
You may be running your mower and realize your engine is no longer giving you the power required to cut your lawn.
If this is happening to you, have a small engine mechanic check and perform tests on your engine to identify any potential problems causing your engine to not give the power you need.
11. Ground Speed is Too Fast
Your engine can get overloaded when mowing at fast speeds causing your lawn mower to give you a bad cut. Just like I mentioned above, an engine that doesn’t give you enough power can result in a bad mower cut.
Know your mowing conditions and adjust your speeds accordingly to not bog down your engine. When mowing tall, wet, or thick grass, you must operate at slower speeds.
Additionally, slow down when operating on inclines. Mowing at too fast of speed can cause your mower to not cut all the grass or it ends up pushing the grass over instead of cutting it.
12. Incorrect Overlapping of Paths
Overlap your mowing paths to not leave strips of grass between each pass. If you have a new mower, this can take some time to get right.
You want to space your paths so you can save time and not keep mowing over the same section twice. It takes a little practice with your mower to get it just right.
13. Mower Deck is Damaged
If you accidentally run into a fence, tree, pole, or another item, you can damage the deck shell. This can give your mower an uneven cut if it is not corrected.
If you are unable to fix your deck shell, you will have to replace it with a new shell.
If you need a deck shell replacement, I recommend contacting your Simplicity lawnmower dealership and getting a quote for a replacement deck shell along with the labor charge to swap all the components over to a new deck shell.
Compare this with a complete deck replacement. You may be surprised to find there isn’t a large price difference. With these two price quotes, you can make the right decision for you based on price and your Simplicity mower’s condition.