Skip to Content

12 Reasons a Spartan Mower Has a Bad or Uneven Cut

No one likes to make an investment in a mower to find it is no longer giving you a nice cut. There are many items that can easily be repaired or replaced so you can get the cut you desire.

A Spartan lawn mower has a bad or uneven cut due to uneven tire pressures; a dull, worn, or bent mower blade; an unbalanced mower blade; a plugged mower deck; a damaged spindle; a worn bearing in the spindle housing or pulley; a worn deck belt; or damaged deck shell.

The incorrect operation of a Spartan zero turn can also affect the cut. The mowing paths must be properly overlapped. Running the engine speed too slow or operating the mower with too fast of a ground speed can produce an insufficient cut.

Take caution when working on the mower and mower deck. Ensure the spark plug wire and the ignition key are removed before troubleshooting and performing any repairs. Take all safety precautions as outlined in the operator’s manual.

Spartan lawn mower has a bad or uneven cut

This post may include affiliate links. Purchases made through these links may provide a commission for us, at no extra cost to you. As an Amazon Associate, we earn from qualifying purchases.

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.

Troubleshoot: Spartan Mower Deck is Cutting Uneven

  • Check for a low tire pressure
  • Check for dull or worn mower blades
  • Check for a bent mower blade
  • Make sure the blade is correctly installed and balanced
  • Clean a plugged mower deck
  • Check for a bent blade spindle or worn spindle bearing
  • Inspect the deck belt or pulleys for wearing
  • Ensure the engine speed sufficient
  • Slow down the ground speed
  • Make sure the mowing paths are overlapped correctly
  • Inspect the mower deck shell for damage
  • Inspect the lawn conditions

Reasons Your Spartan Lawn Mower is Cutting Uneven

Insufficient Tire Pressures

Before you check anything on your mower, first check your tire pressures. A Spartan mower that is cutting unevenly can be from something as simple as low tire pressures.

Check the pressures in both drive tires to ensure they are to an efficient pressure as shown in your operator’s manual.

The tire pressures should be the same for both the left and right drive tires. If one tire pressure is lower, the deck on the mower will sit unleveled resulting in a bad cut.

If your mower uses air-filled caster wheels, the pressures will also need to be checked.

Failing to check the tire pressures first may cause you to make unnecessary adjustments to your mower deck that will have to be reversed once you realize your tire pressures are incorrect.

Dull or Worn Mower Blade

A bad cut can be caused by a mower blade with a dull edge or the wearing of the sail and blade tips. Unfortunately, wearing cannot be avoided. Mower blades are wear items that must be sharpened or replaced to ensure a good cut.

Blades naturally wear. They will wear faster in sandy lawns than in thick lush lawns since the suction of the mower deck pulls dirt into the deck. More dirt will be pulled from scarcely covered grass lawns.

Dull Spartan mower blades will cause the mower to beat up the grass and not give it a nice precise cut. This is often the case when a lawn’s grass tips turn brown a couple of days after you mow it.

Worn Spartan mower blades may leave a strip of grass between the mower blades when the blade ends are rounded.

They can also prevent the mower from giving you a nice even precise cut when the blade sails are worn. The blade sail is the high side of the blade that is used to create air movement under the mower deck.

This air movement, in combination with the deck shell and baffles under the deck, creates a suction to lift the grass tall while the blade passes by to cut it evenly.

It’s important to check your Spartan mower blades regularly for wear. Sharpen blades that have dull cutting edges.

If the blade is thinner on the blade sail than it is in the middle of the blade or the blade ends are rounded, it’s time to replace it with new mower blades.

Bent Mower Blade

An uneven cut can be the result of a bent mower blade. A blade becomes bent when it hits a solid or stationary object like a tree root or rock. Take time to look at the blades for damage.

If you find the blades have chips or gouges in the blade edge, you can remove small nicks by sharpening your blades. You may have to replace the blades with new blades when the gouges are too large to remove.

Continue to check for a bent blade. When the bend isn’t significant and it’s difficult to visually see a bend, follow one of these methods to determine whether the mower blade is bent:

Without removing a mower blade:

  • Park your mower on flat ground
  • Remove the key and spark plug boots to prevent the mower from turning on.
  • Take the measurement from the tip of one end of the blade to the ground. Record the measurement.
  • Turn the blade 180 degrees to measure the opposite end of the blade. Record the measurement.
  • If there is over and 1/8″ variance from one blade end to the other blade end, replace with a new blade.
  • Repeat this step with each blade on your Spartan lawn mower.

By removing a mower blade:

  • Park your mower on flat ground
  • Remove the key and spark plug boots to prevent the mower from turning on.
  • Gain access to the underside of your deck. Remove the mower blade.
  • Lay the old blade on top of a new blade. If the blades don’t fit together and leave any gaps, you must install a new mower blade.

If you find a bend, you will need to check the spindle bearing for damage. The bearing can fail when there is a significant impact on the blade.

NEVER attempt to straighten a mower blade. Doing so will compromise the metal and make it more prone to crack. A cracked mower blade is hazardous when spinning at high rates of speed.

Incorrectly Installed or Unbalanced Mower Blades

The sail of the blade, this is the high side, must be installed facing upward toward your mower deck. Installing your blades upside down will tear up your grass and cause potential damage to the blade spindles.

Make sure your blades are balanced before you install them. Unbalanced blades can cause an uneven cut and send a vibration through your mower. Read more about mower blade installation here.

Plugged Mower Deck

Spartan mower decks are designed to use the area under the mower deck, the baffles, and the air movement created by the mower blades’ rotation to form a suction. This suction stands the grass tall while the blade cuts the grass for an even cut.

When the deck is plugged, it can’t create the suction needed for a quality cut. The area required under the deck is greatly reduced when grass gets packed under the deck.

You must check and scrape your deck regularly. You’ll have to scrape it more often when cutting wet grass. Wet grass tends to stick to the mower deck and leave clumps in your yard.

Some Spartan lawn mower owners choose to use a spray meant for mower decks to prevent some of the debris from sticking to your deck. This spray helps, but it will not prevent all of the grass from sticking.

Bent Blade Spindle or Worn Spindle Bearing

Check the blade spindles for a bent spindle or a damaged bearing. Again, make sure your spark plug boot(s) is removed and the ignition key is removed for safety.

With a pair of heavy gloves, grab a hold of each end of your mower blade. Rock the blade up and down and check for movement.

If you feel movement or hear a knock, you have a bad bearing in the spindle housing or a bent spindle. You will need to repair or replace the spindle housing.

Bad Mower Deck Belt or Pulleys

Turn each pulley on the deck slowly to see if you can feel any resistance or hear any noise. Replace any pulleys that don’t rotate smoothly or you hear a noise coming from the bearing.

Make sure your belt is in good condition without cracks and wear. The belt must run securely around the pulleys.

Engine Speed is Too Low

Run your engine at full throttle when your mower deck is engaged. Too slow of an engine speed will not give your deck enough power to rotate the mower blades to give you the fast blade tip speeds required for a quality cut.

Ground Speed is Too Fast

Adjust your ground speed when mowing thick, tall, or wet grass. Cutting grass in these types of conditions puts extra work on your engine so slowing your groundspeed will reduce the load on the engine.

When your engine and deck are unable to handle the load on the mower, it may not provide a good cut. Mowing too fast can also cause your mower to not be able to create a good suction and end up pushing over some grass.

Incorrect Overlap

Sometimes the cutting problem is the fault of the operator. When mowing stripes in your lawn, you need to overlap each pass so you don’t miss any sections of grass and leave strips of grass in the lawn.

I made this mistake when I attempted to mow my lawn with the least amount of passes to save time. While I cut down on time, I did find I left strips of grass on my lawn.

Damaged Mower Deck Shell

A lot of time is put into the design of a Spartan lawn mower deck as it is an important part of achieving the right airflow to create a quality cut. A deck shell can get tweaked by running your mower into objects like trees, rocks, and other hard surfaces.

You can attempt to repair a deck shell to try to get it back in place. If the deck is not repairable, you must replace the deck shell or purchase a complete mower deck. Before you make the decision on which option to choose when repairing the mower deck, talk to your Spartan mower dealership and get two quotes.

One quote for a deck shell and labor to swap all of the components from the old deck to the new deck. The other quote is for a complete deck replacement. Make an educated decision on the option that’s best for you while taking in the age of your lawn mower.

Your Lawn is Uneven

When your lawn is uneven and bumpy, your mower deck can scalp the lawn. For a nice-looking cut, it will help to roll your lawn to smooth it out.