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Troubleshoot 6 Common Zero Turn Mower Deck Problems

When you own a zero-turn mower long enough you’re likely to run into a performance or mechanical issue.

To help you identify the problem you are having with your zero-turn mower deck, I have put together charts listing causes and solutions to common mower deck problems. You will also find links to guides that provide more detail.

Before working on the mower deck, take the safety precautions found in your operator’s manual.

This includes parking on a flat-level surface, removing the ignition key, removing the spark plug wires, and waiting for all parts to stop moving.

Zero turn mower deck problems

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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.

1. Bad or Uneven Cut

There are many items that can cause your mower to not provide you with a good quality cut.

The first thing to check is the tire pressure. Something as simple as a low tire can cause the mower deck to sit unleveled.

You’ll also need to check the condition of the belt, the condition of the mower deck parts, a plugged mower deck, and the mowing conditions.

For More Information Check Out:
Reasons Your Zero Turn Has a Bad or Uneven Cut

Dull or worn mower bladesSharpen the mower blades. Replace blades that are extremely worn where the blade sails are thinner than the center of the blade or the blade ends are worn and rounding.
Bent mower bladeReplace a bent mower blade.
Blade installed wrongMake sure the blades are installed with the correct hardware. The blade sails must be pointed upward toward the mower deck.
Bent blade spindleReplace a bent spindle. Inspect the spindle housing for damage.
Bad mower deck belt or bad pulleysReplace a deck belt that is stretched, worn, cracked, or has a glazed appearance. Slowly rotate the pulleys by hand. Replace the pulleys when you feel a restriction, hear a bearing noise, or the pulley is wobbling.
Mower deck is plugged with grass clippings & debrisScrape the mower deck.
Uneven tire pressureCorrect the tire pressures. Make sure they are even on the left and right-hand sides.
Unleveled mower deckLevel the mower deck so the mower deck is level side-to-side. The mower deck sits slightly lower in the front than in the rear. Consult the operator’s manual for exact specifications to level the deck.
Engine speed is too lowWhen engaging the blades, have the throttle set at the highest level.
Ground speed is too fastSlow down when mowing thick, wet, or tall grass. Mowing in these conditions puts extra strain on the engine. Running the mower too fast can end up pushing over some grass instead of cutting it.
Operator errorProperly overlap paths so strips of grass are not left in between passes. Use a small format deck like a push mower to mow ditches and other steep changes in grade.
Zero Turn Has a Bad or Uneven Cut

2. Deck Belt Keeps Coming Off

It can get frustrating to have to stop mowing to install the belt on the mower deck when it keeps coming off.

The condition of the belt, the tension on the belt, a bad pulley, or debris on the deck can all contribute to this problem.

For More Information Check Out:
Belt Keeps Coming Off Your Zero Turn

Worn or loose beltReplace a belt that is loose or worn. This is a belt that may have cracks or a shiny glazed appearance.
Belt keeper or belt guide damageBend or shape belt keepers to their original position. Replace belt keepers that can’t be repaired.
Shredded beltReplace a shredded belt. Identify and repair the item that caused the belt to shred.
Bad spindle housing bearingReplace the spindle housing assembly.
Bad pulley bearingSome pulleys can have the bearing replaced. You will need to replace the whole pulley assembly when this isn’t possible.
Worn idler tensioner bracket or springReplace a worn idler bracket or weak spring.
Debris interfering with belt tensionRemove leaves, mud, wood chips, and stones building up under the tensioner that keeps it from moving.
Debris stuck in the pulley groovesRemove debris and dirt from the pulley grooves
Oil or rust on the beltReplace the deck belt.

3. Mower Deck is Vibrating

There is always going to be some vibration when operating your mower. Mowing uneven ground can contribute to the amount your mower is vibrating or shaking.

When you notice the mower deck vibration is more severe than usual, it’s time to check the deck components. This includes the deck belt, pulleys, spindle housings, blade shaft, and blades.

For More Information Check Out:
Your Zero Turn is Shaking and Vibrating

Loose or missing engine mounting boltsSecure engine bolts and replace any missing bolts
Clutch is badReplace the clutch
Unbalanced or damaged mower bladesReplace any damaged blades and make sure they are balanced.
Material wrapped around the blade spindleRemove all debris and items wrapped around the blade shaft. Check for spindle damage.
Bad spindle housing bearingsReplace the bearing in the spindle housing or replace the whole spindle housing assembly
Worn pulleys or deck beltReplace any damaged or worn belts and pulleys
Debris lodged in mowerCheck over your mower deck and mower for any place small items can be stuck in your mower. Remove these foreign materials.
Reasons Your Zero Turn Mower is Vibrating

4. Mower Blades Won’t Engage

Most zero-turn mowers use an electric clutch. The clutch solenoid requires power to turn the blades.

Check for items that can keep the clutch from working including the battery, PTO switch, safety switch, fuse, and the clutch itself.

It’s also necessary to check the belt and items that can affect the tension on the belt.

For More Information Check Out:
Zero Turn Mower Blades Won’t Engage or Turn On

Worn mower deck beltReplace a belt that is worn, cracked, or has a shiny glazed appearance.
Belt falls off the pulleysReplace worn or damaged deck parts including a worn idler arm, worn spring, or bad pulleys. Replace a stretch mower deck belt.
Bad PTO switchReplace the PTO switch.
Bad clutchReplace the clutch. On a manual engagement clutch, replace a worn clutch cable, lever, springs, and linkages.
Weak batteryTest the battery and place it on a charger if the reading is less than 12.7 volts for a 12-volt battery. Replace the battery when it won’t hold a charge.
Bad safety switchReplace the safety switch.
Blown fuseReplace the fuse with one of the same amperages. If it continues to blow, have a mechanic identify the root cause of the problem.
Zero Turn Mower Blades Won’t Turn On or Engage

5. Mower Deck Builds Up with Grass Clippings

When the mower deck builds up with grass, it will no longer have a sufficient area for good airflow. It will also cause the engine to work harder to turn blades through a deck packed with grass.

To minimize grass buildup, you can try to use a deck spray like this one by DuPont. While this spray won’t keep all grass from sticking, it will reduce the amount of grass that sticks.

It’s important to keep the area under the deck free of debris and grass clippings by routinely scraping the mower deck.

Mowing wet grassOnly mow dry grass.
Mowing at a low engine speedMow at a high throttle to create better air movement under the deck.
Mowing long grassMow more frequently to avoid cutting long grass. If the grass is long, you should double or triple-cut the lawn.
Reasons Grass Keeps Building Up Under a Zero Turn Mower Deck

6. Mower Deck is Squealing

When you hear an odd noise or a squealing coming from the mower deck, the first thing to look at is the belt. If the belt has slipped and is stuck on the deck, reinstall the belt correctly around the pulleys.

Next check the pulley and spindle housing bearings. This noise could be an indication of a bearing failure.

Belt slipped and stuck between the belt guides.Reinstall the belt correctly. Replace the belt if it is worn.
Broke tensioner spring Replace the tensioner spring.
Material wrapped around the blade shaftRemove any foreign objects wrapped around the blade shaft.
Bad spindle housing bearingReplace the spindle housing assembly. You may able to replace the bearing on some zero-turns.
Bad pulley bearingReplace the pulley assembly. You may be able to replace the bearings in some zero-turn pulleys.
Zero Turn Mower Deck is Squealing & Making Noise