Riding Mowers & Tractors: Why is my riding mower not cutting evenly?

If your riding lawn mower is cutting the grass unevenly, start by checking the pattern of the cut. If the cut looks like slanted stair steps, inflate the tires to the manufacturer's recommendation and level the mower deck. If you see alternating stripes of taller and shorter turf, slow down while mowing--mowing too fast can cause those stripes. If slowing down doesn't fix the stripes, sharpen or replace the mower blades. Sharpening or replacing the mower blades is also the answer if grass tips look ragged or tattered instead of cleanly cut.

Blade vibration also causes an uneven cut. To eliminate vibration, replace unbalanced blades and worn mandrels. Replace a worn blade belt because a worn belt won't spin the blades correctly. Worn deck idler pulleys can also cause vibration, so replace any deck pulleys that don't spin freely. Check the mower deck for damage and replace the deck if it's bent. Finally, tune up the mower engine if it doesn't run smoothly when mowing.

riding mowers & tractors

THESE REPAIRS MAY HELP SOLVE YOUR RIDING MOWERS & TRACTORS PROBLEM

JC-RM-Replace-the-riding-mower-mandrel-assembly

Replace the riding mower mandrel assembly

The mandrel assembly attaches to the deck and spins the blade to cut grass. A blade won't move if the mandrel locks up. A damaged mandrel causes mower deck vibration and uneven cutting. Examine the mandrels regularly and replace any damaged mandrels.

Riding mower mandrel assembly

Find the required part specific to your product.

RG-RM-Replace-a-Riding-Mower-Mandrel-Assembly-Intro-Image
March 1, 2017By Lyle Weischwill

How to replace a mandrel assembly on a riding lawn mower

If the blade shaft on your riding lawn mower vibrates or won't spin the blade, the mandrel might be worn or damaged. This DIY repair guide and vidoe explain how to replace a riding lawn mower mandrel assembly in just 6 steps.

Repair difficulty
Time required
 30 minutes or less
JC-RM-Level-the-mower-deck-on-a-riding-mower

Level the mower deck on a riding mower

A tilted mower deck can cause uneven cuts. Park the lawn tractor on a flat surface and inflate all 4 tires evenly. Lower the deck to the cutting position and position the blades sideways. Measure the height of the cutting blade outer edges. Adjust the mower deck hangers to level the mower blades for an even cut. Watch our How to level a riding lawn mower deck for an even cut video for detailed mower deck leveling instructions.

Level the mower deck on a riding mower

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JC-RM-Replace-a-riding-mower-blade

Replace a riding mower blade

A bent mower blade won't cut grass evenly and may cause mower deck vibration. Dull blades leave ragged edges on cut grass. Inspect mower blades regularly and replace a riding mower blade if it's damaged, bent or dull.

Replace a riding mower blade

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RG-RM-Replace-a-Riding-Mower-Blade-Intro-Image
January 1, 2015By Lyle Weischwill

How to replace a riding lawn mower blade

If brown, tattered grass tips make your lawn look sick, one or more blades on your riding mower could be dull or bent. This repair guide and video show how to replace a riding mower blade in 30 minutes or less.

Repair difficulty
Time required
 30 minutes or less

RG-RM-Replace-a-Zero-Turn-Riding-Mower-Cutting-Blade-Intro-Image
January 1, 2015By Lyle Weischwill

How to replace a cutting blade on a zero-turn riding mower

If your grass looks tattered after mowing with a zero-turn riding, the problem could be a dull or damaged blade. This easy-to-follow repair guide and video explain how to replace a blade on a zero-turn riding lawn mower.

Repair difficulty
Time required
 15 minutes or less
JC-RM-Replace-the-riding-mower-blade-belt

Replace the riding mower blade belt

The blade belt spins the blades to cut the grass. A worn or broken drive belt won't spin the cutting blades so your mower won't cut the grass. A worn blade belt can also cause mower deck vibration or uneven cuts. Examine the blade belt regularly and replace it if it's worn or broken.

Riding mower blade belt

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RG-RM-Replace-a-Zero-Turn-Riding-Mower-Blade-Belt-Intro-Image
January 1, 2015By Lyle Weischwill

How to replace the blade belt on a zero-turn riding mower

If the blades won't spin on a zero-turn riding mower, the problem could be a broken blade belt. Replace a broken or worn blade belt on a zero-turn riding lawn mower by following the steps in this DIY repair guide and video.

Repair difficulty
Time required
 30 minutes or less

RG-RM-Replace-a-Riding Mower-Blade-Drive-Belt-Intro-Image
January 1, 2015By Lyle Weischwill

How to replace a riding lawn mower blade drive belt

If the blades on your riding lawn mower don’t spin fast enough—or don’t spin at all—the blade drive belt could be worn out or broken. This repair guide and video show how to replace a blade drive belt in less than an hour.

Repair difficulty
Time required
 45 minutes or less
JC-RM-Tune-up-the-riding-mower-engine

Tune up the riding mower engine

The engine tune-up includes routine maintenance for a riding lawn mower or tractor. Engine performance suffers if you don't regularly tune up the engine. A poor-running engine may stall when you try to drive the mower. You may notice uneven cuts if the engine doesn't run smoothly when you're mowing grass. Routinely tune up the engine by replacing the engine oil, oil filter, air filter, fuel filter and spark plug. The tune-up also includes checking the ignition, carburetor, battery, throttle and choke controls, as well as cleaning the engine cooling fins.

Tune up the riding mower engine

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RG-RM-Replace-a-Riding-Mower-Fuel-Filter-Intro-Image
January 1, 2015By Lyle Weischwill

How to replace a riding lawn mower fuel filter

If your riding lawn mower’s engine runs rough or won't run, the fuel filter could be dirty. This repair guide and video show how to easily replace the fuel filter on your riding lawn mower in 15 minutes.

Repair difficulty
Time required
 15 minutes or less

RG-RM-Replace-a-Riding-Mower-Spark-Plug-Intro-Image
January 1, 2015By Lyle Weischwill

How to replace a riding lawn mower spark plug

If your riding lawn mower engine runs rough or is hard to start, it might be because the spark plug is damaged. This DIY repair guide and video show how to replace the spark plug on a riding mower in 15 minutes or less.

Repair difficulty
Time required
 15 minutes or less

RG-RM-Replace-a-Riding-Mower-Air-Filter-Intro-Image
March 1, 2017By Lyle Weischwill

How to replace the air filter on a riding lawn mower

If your riding lawn mower runs rough or stalls after starting, the air filter could be dirty. This DIY repair guide and video show how to replace a clogged riding mower air filter in less than 15 minutes.

Repair difficulty
Time required
 15 minutes or less
JC-RM-Replace-the-mower-deck-on-a-riding-mower

Replace the mower deck on a riding mower

The mower deck houses the cutting blades, mandrel pulleys and blade drive belts. You may see uneven cutting if the mower deck gets damaged because the deck. Severe rust can corrode the deck, causing holes in the deck. Replace the mower deck if it's damaged or there's a lot of rust.

Mower deck on a riding mower

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RG-RM-Remove-a-Zero-Turn-Riding-Mower-Mower-Deck-Intro-Image
January 1, 2015By Lyle Weischwill

How to remove the mower deck on a zero-turn riding mower

Need to remove the mower deck on a zero-turn riding lawn mower but aren't sure how? This DIY repair guide and video show how to remove the mower deck in 6 easy-to-follow steps.

Repair difficulty
Time required
 15 minutes or less
JC-RM-Replace-the-riding-mower-deck-idler-pulley

Replace the riding mower deck idler pulley

The deck idler pulley tightens the blade belt against the blade pulleys to spin the blades when you shift the blade engagement lever to engage the blades. You might need to replace the riding mower deck idler pulley if the blades don't spin. A worn idler pulley can also cause uneven cuts and mower deck vibration, so check the idler pulley if you notice these symptoms. Replace the deck idler pulley if it's worn or broken.

Riding mower deck idler pulley

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Symptoms common to all riding mowers & tractors

Choose a symptom to see related riding mower and lawn tractor repairs.

Main causes: punctured tire or inner tube, leaky valve stem, damaged wheel rim
Main causes: worn or broken ground drive belt, bad seat switch, transaxle freewheel control engaged, transaxle failure, dirty carburetor
Main causes: shift lever needs adjustment, neutral control needs adjustment
Main causes: worn or broken blade belt, broken belt idler pulley, blade clutch cable failure, bad PTO switch, damaged mandrel pulleys
Main causes: damaged cutting blade, worn deck pulley, damaged mandrel pulley, loose fasteners on mower deck components
Main causes: engine overfilled with oil, leaky head gasket or sump gasket, damaged carburetor seals, cracked fuel pump, broken fuel line
Main causes: clogged carburetor, damaged flywheel key, dirty spark plug, stale fuel, improper valve lash, engine needs a tune up
Main causes: faulty battery, bad alternator
Main causes: unlevel mower deck, dull or damaged cutting blades, worn mandrel pulleys, bent mower deck, engine needs tune up

Repair guides common to all riding mowers & tractors

These step-by-step repair guides will help you safely fix what’s broken on your riding mower or lawn tractor.

January 1, 2015
By Lyle Weischwill
How to replace a riding lawn mower rear tire

Your mower can’t run on a damaged rear tire. Here’s how to install a new one.

Repair difficulty
Time required
 60 minutes or less
January 1, 2015
By Lyle Weischwill
How to replace a riding lawn mower blade

If a blade on your mower is dull or bent, replace it following the steps in this repair guide.

Repair difficulty
Time required
 30 minutes or less
January 1, 2015
By Lyle Weischwill
How to replace a riding lawn mower fuel filter

Help your mower run better by replacing the fuel filter during your riding mower's annual tune-up.

Repair difficulty
Time required
 15 minutes or less

Articles and videos common to all riding mowers & tractors

Use the advice and tips in these articles and videos to get the most out of your riding mower or lawn tractor.

August 6, 2020

How to remove a lawn mower blade using a removal tool

By Sears PartsDirect staff

Learn how a blade removal tool makes replacing the blade easier and safer

April 9, 2019

Riding mower parts and supplies to stock up on video

By Sears PartsDirect staff

Keep these 6 things on hand to keep the mower season running smoothly.

January 1, 1970

How to tell if a fuse is blown

By Lyle Weischwill

Learn how to tell whether a fuse is blown