Zero-Turn Mower Loses Power When Blades Are Engaged

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If your zero-turn loses power when the blades are engaged, it can be frustrating and annoying, especially if you have a lot of mowing to do.

In this article, I share 10 common reasons why your zero-turn mower loses power when blades are engaged and troubleshooting tips that you can follow to diagnose and fix these problems.

Reasons Why Your Zero-Turn Mower Loses Power When Blades Are Engaged

Some of the reasons why your zero-turn may lose power when blades are engaged may include:

  • Dull Blade
  • Worn out blade spindle bearings
  • Clogged muffler
  • Clogged fuel filter/fuel lines
  • Dirty carburetor
  • Dirty underside
  • Loose/worn mower belt

Tools You May Need for This Job

  • Torque wrench
  • Ratchet
  • Work gloves.
  • Socket Wrench
  • Cordless Impact Gun (Optional)
  • Carburetor Cleaner
  • Compressed Air
  • Safety glasses

Zero-Turn Mower Loses Power When Blades Are Engaged: Possible Causes and Fixes

1.  Dull Blade

When the blade is dull, it has to work harder to mow through the grass which can cause the mower engine to lose power when blades are engaged. 

This will further affect the functionality and performance of your zero-turn mower.

Diagnosis

  • Inspect the blades to see if they are dull.  

Fix

How To Remove and Change Zero-Turn Mower Blades

Here are some tips on how to remove your zero-turn mower blades:

Step 1.  Get the Required Tools

The first step to take is to get the needed tools for blade removal. These tools include a cordless impact gun (optional), safety glasses, torque wrench, ratchet and work gloves.

Step 2. Remove Spark Plug Wires

It is advisable to take off the ignition key and spark plug boots of your zero-turn mower. 

This will prevent the mower from starting when you are working under the cutting deck. In addition, set the parking brake.

Make use of safety glasses to protect your eyes and work gloves to shield your hands from the sharp edges of your blades.

Step 3. Take Off Zero-Turn Mower Blades

Use ratchets and sockets to remove the zero-turn mower blades. You can also use a cordless impact gun if they do not come off easily.

You can also attempt to remove stubborn bolts by placing a block of wood over the head of the bolt. 

Hit the block with a hammer to loosen the bolt so that you can turn it. Take off the washers, bolts, and blades that the mowing machine may use. 

Re-install the zero-turn mower blades and components in the opposite order you took them off.

If you want to re-use these blades, ensure that you sharpen and balance them before re-installing.

2. Worn Out Blade Spindle Bearings

Worn-out blade spindle bearings can be a reason why your zero-turn mower may lose power when blades are engaged. This issue is common with Exmark zero-turn mowers.

The bearings enable the blades to freely spin on their axis. If it is worn out, it can cause friction and may make your mowing machine lose power.

Diagnosis

  • Examine if the blades can freely spin on their axis. If not, it means that the bearings in the blade spindles are worn out.

Fix

  • Replace worn-out blade spindle bearings.

3. Clogged Muffler

The function of the muffler is to expel the burned gas and other vapors. If it is blocked by grass, dirt and other debris, it can cause your mower to lose power.

Diagnosis

  • Check the muffler for debris, dirt and other fluids.
  • If you notice a colored smoke that comes out of your zero-turn mowing machine, then there is a high chance that the muffler is clogged.

Fix

  • Replace the clogged muffler for a new one.

4. Clogged Fuel Filter/Fuel Lines on The Zero-Turn Mower

Dirt and substances left behind by running old gas can cause the fuel filter and fuel lines to become blocked. This can cause fuel restriction and make the mower lose power.

Diagnosis

  • Check the fuel filter for clogs. If you notice that enough gas isn’t passing through the fuel filter or it is not enough to run at full throttle, it indicates that the fuel filter needs a replacement
  • Inspect for clogs in the fuel lines by starting and stopping the fuel flow, using the fuel shut-off valve situated on the bottom of the fuel tank.
  • Take off the furthest end of the fuel tank of the fuel line (just one section) and place it in the container.
  • You can also check other sections of the fuel line for clogs. If the line is cracked or dry, you may need to replace it with a new fuel line.

Fix

  • Replace the fuel filter if it is in bad condition.
  • To fix clogged fuel lines, remove the section of the line and spray a carburetor cleaner into the line to help loosen the clogs.
  • Blow compressed air through the line to eliminate obstructions.
  • Replace the fuel line if it is dry or cracked.

5. Dirty Carburetor

The carburetor can regulate the right amount of air and gas that should be allowed in the cylinder to form combustion.

Dirt and other substances left behind by old gas can cause the carburetor to be dirty. This will cause the mower to lose power when the blades are engaged.

Diagnosis

  • Check the carburetor for dirt and other substances left behind by the old gas.

Fix

  • Clean the carburetor or replace it if it is in bad condition.

6. Dirty Underside

A dirty underside might be one of the reasons why your zero-turn mower may lose power when the blades are engaged.

This issue is common with Husqvarna zero-turn mowers. Whenever the blade is engaged, the underside rotates on a crankshaft to mow the grass. 

The mower engine can shut off if there is an interference in this rotation.

Diagnosis

  • Inspect the connection of the crankshaft to see if it rotates freely. If the crankshaft’s connection does not rotate freely, it indicates that the mower’s underside is dirty.

Fix

  • Clean the blade so that it will be free of debris, dirt and grass. 

7. Loose or Worn Mower Belt

When mower belts are not properly routed, they will cause issues when the blades are engaged. 

In addition, a loose belt can also slip off the pulleys, causing the mower to lose power.

Diagnosis

  • Examine the belt for wear, cracks, breaks or slippage. 

Fix

  • Replace the belt if it is in a bad condition.

8. Bad Pulleys

The mower belt drives the pulleys, which in turn moves spindles. 

If the pulleys cannot turn freely, they would cause the engine to lose power. This will affect the operation of your zero-turn mower.

Diagnosis

  • Check pulleys if they are moving freely. If not, it indicates that the pulleys are bad.

Fix

  • Replace the pulley if it is sticky or damaged.

9. Dirty Air Filter

It is also important to check the air filter if your zero-turn mower is losing power. 

The mower engine requires air to run and when it no longer gets the air it requires, the engine may lose power.

Diagnosis

  • Take off the air filter from the air filter housing and check for dirt on it

Fix

  • Clean or replace the air filter if it is in bad condition.

How to Clean a Paper Air Filter

Here are some tips to follow while cleaning a paper air filter:

  • Take off the air filter from the mower’s housing.
  • Use a dry cloth to clean the dirt that is in the housing. Make sure that the dirt does not enter the air intake.
  • Tap the filter against a solid surface to remove dirt.
  • Hold the air filter to a light source and ensure that you can observe a light that shines through the paper element. If you can’t see light shine through it, it means that you should get a new one.
  • Reinstall the air filter and attach the air filter’s housing cover

How to Clean a Foam Air Filter

Here are some tips to follow while cleaning a foam air filter:

  • Take off the air filter from the mower’s housing.
  • Use a dry cloth to clean any dirt that is in the housing. Make sure that the dirt does not fall into the air intake.
  • Check the filter for tears, dark spots or if it is brittle or dry. Replace the filter if you notice these signs.
  • Use water and mild dish soap to wash the foam filter. Rinse to take off the soap from the foam filter.
  • Lay it flat to dry. You can also sun dry it to fasten its drying process.
  • Coat your filter with a foam air filter oil once it is totally dry.
  • Reinstall the air filter and attach the air filter’s housing cover.

Please note: It is advisable to replace the air filter if it is in a bad condition.

10. Faulty Spark Plug

For air and gas to be ignited, the mower’s spark plug must be in a good condition and correctly adjusted.

Over time, it may wear out and it will no longer have enough power to ignite gas and air This can make the zero-turn tp lose power when blades are engaged..

Diagnosis

  • Use a socket wrench to remove the spark plug.
  • Clean the spark plug with a wire brush.
  • If the firing end is covered with carbon, it means that the spark plug needs to be changed.

Fix

  • Replace the faulty spark plug with a new one.

How To Change A Spark Plug on a Zero-Turn Lawn Mower

Here are some tips on how to change a spark plug on your zero-turn mower:

  • Put your mowing machine on a level and flat surface. Turn off the mower and ensure that the engine is cool. Remove the ignition key and engage the parking brake.
  • Unplug the spark plug cables from the spark plug.
  • Use a spark plug socket to remove the old spark plugs
  • Gap the new spark plug properly and make use of a feeler gauge or gap tool to set the spark plug gap. Homeowners that own a Cub Cadet Ultima zero-turn mower can set the spark plug gap at .030 inches.
  • Reinstall your new spark plugs. Make sure that you do not overtighten your spark plugs.
  • Reconnect the spark plug cables.

Conclusion

Some of the possible causes why your zero-turn mower may lose power when blades are engaged include a faulty spark plug, dirty carburetor, dirty underside, dirty air filter, worn/loose belt and clogged fuel filter.

Follow the troubleshooting guide and recommended fixes in this article to identify and solve the issues.

If the problem persists, it is advisable to contact a technician to help you fix the problem.