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Sun Joe Electric Mower Has a Bad or Uneven Cut (9 CAUSES)

You may notice your lawn mower is no longer cutting like it once did. It may be leaving stair step cuts or it may begin scalping the lawn. There are many items that can be easily fixed to achieve a better cut quality.

A Sun Joe electric mower may have a bad or uneven cut due to a damaged wheel; dull, bent, or worn mower blade; wrong mower deck height; fast ground speed, or plugged mower deck.

Follow all safety precautions found in your operator’s manual including shutting off the mower, removing the battery, removing the safety key, and waiting for all parts to stop moving before troubleshooting.

Mower is cutting uneven

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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.

Your Sun Joe Electric Battery-Powered Mower Cuts Uneven

1. Damaged Wheel

Before you check anything else, check the wheels on your mower. A damaged wheel can cause the mower to sit unleveled causing your cut to be uneven.

The wheels on an electric push mower can come loose or become damaged causing the mower not to sit level. Inspect the wheels. Tighten any loose hardware and replace any damaged wheels.

2. Mower Blade is Worn or Dull

Once you have confirmed the wheels are in good condition, look at the Sun Joe mower blade. When the blade becomes worn, it won’t make a good cut through the grass. A worn blade will just end up tearing the ends of the grass.

You’ll notice this when your lawn turns brown a day or two after you mow. The tips of the grass turn brown because the grass is being beaten up and torn by a dull blade.

Next time you experience a lawn where the tips turn brown, grab a handful of grass and take a look at the tips. Do they have little tears in them? If so, this is a sign your Sun Joe mower blade may need sharpening or replacing.

Remove your Sun Joe electric mower blade and sharpen it with a file if they are still in good condition.

When the blade isn’t in good condition because it is extremely worn, has gouges, has rounded blade ends, or the blade sail is thinner than the center of the blade, replace it with a new mower blade.

Balance the mower blade

Make sure the blade is balanced with equal weight on both ends of the blade. A blade can become out of balance when the blade has become unevenly worn by sand that gets sucked into the underside of the mower deck.

Another way a Sun Joe blade becomes uneven is during the sharpening process. When more metal is removed from one end of the blade than the other, the blade becomes unbalanced.

Check your blade balance using a blade balancer. A balancer is relatively inexpensive. It’s worth the investment because an unbalanced blade may cause significant damage to your Sun Joe mower.

Another method to check for 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.

3. Mower Blade is Bent

When your blade impacts a solid object like a rock, stump, or toy, it can bend causing your Sun Joe mower to give a bad cut.

To prevent damage to the blade, it’s a good idea to walk the lawn to make sure there’s nothing in the way that you may run over and damage the mower.

A bent blade will cause an uneven cut. It can also cause your mower to start vibrating. Sometimes a bent blade is obvious and sometimes not so the best way is to remove the blade.

Make sure your mower is parked on a flat-level surface and remove the battery pack(s). Wait for all moving parts to stop moving before working under the mower deck.

  • Check for a Bent Mower Blade By Removing the Blade
    Remove the blade and lay it on top of a new Sun Joe mower blade. This is the best way to verify whether or not your blade is bent. Even a very slight bend can cause a bad cut.

NEVER attempt to straighten a bent mower blade to reuse it. When you do this, the metal is compromised and becomes weakened.

It is possible for the weakened area to break off and fly out of your mower deck at high speeds. This could cause injury or damage to people, pets, or objects in the area.

4. Mower Blade is Installed Incorrectly

You can damage your Sun Joe electric mower by using the wrong blade or installing it incorrectly. Make sure the blade is installed with the sail in the up position.

The sails are the high sides of the blade that help create air movement to toss the grass. When the blade is installed with the sail facing the ground, damage can occur to the blade motor.

Instead of cutting the grass evenly, the upside-down blade will beat up and tear your grass. It can potentially hit high spots in the ground causing impact to the blade and potential damage to the motor.

5. Blade is Not Tight

When the blade is not securely attached, the blade will fail to rotate causing your electric mower not to cut the grass. Refer to your operator’s manual for the right torque specs for the blade bolt and tighten accordingly.

6. Cutting Height Setting

You can end up with an uneven cut when your mower deck is set too low and it isn’t able to handle the amount of grass without compromising the cut.

Adjust the mower deck height to a higher setting when cutting thick tall grass so you don’t overwork the motor.

When the grass is tall or thick, double-cut or triple-cut your lawn. This is done by setting the mower deck to the highest setting for the first cut. Lower the deck height for each additional cutting until you achieve the cut you want.

7. Mower Deck is Plugged with Grass

Your Sun Joe electric mower will give you a bad cut when your mower deck is plugged with grass. This is because there is no longer sufficient area under your deck for the blade to create the airflow needed to give a good precise cut.

The mower deck and mower blade are designed to work together to create suction to lift grass so the blade can pass by and provide a nice even cut.

A plugged mower deck can also wear on your motor and cause it to work harder when having to turn the blade through the grass clippings under the deck.

Regularly clean the mower deck to keep it free of grass and dirt buildup using a deck scraper or wire brush. Avoid cutting wet grass. Wet grass will clump and stick to your mower deck.

8. Ground Speed is Too Fast

Your ground speed needs to be adjusted to your mowing conditions to receive a good cut.

If you don’t properly adjust your speeds and move too fast through your lawn, your Sun Joe mower will give you a bad or uneven cut because it may just be pushing over some of the grass instead of cutting it.

Your lawn mower is put under a heavy load when it is cutting thick, tall, or wet grass. You must slow down so your mower is better able to handle the load.

In addition to a bad cut, the motor can become overloaded and cause it to shut off.

9. Uneven Lawn

Check the condition of your lawn. If the lawn is uneven, your Kobalt mower is not going to fix that. You may have ruts and bumps in the lawn so your lawn is no longer even.

I have to roll my lawn every spring after the snow melts to flatten the lawn due to rodents digging tunnels through the yard. Without doing this, I not only get a bad cut but the mower bounces all over the place.

Check your lawn to see if you have any maintenance that needs to be done to keep your lawn flat and in good condition.