Scag Mower Loses Power When Blades Are Engaged

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If your Scag mower loses power when the blades are engaged, it may be as a result of dull blades, a worn belt, a faulty spark plug, a clogged fuel filter, clogged air filters and bad gas.

In this article, I share 10 common reasons why a Scag mower loses power when blades are engaged and proffer solutions to each problem to help you troubleshoot and fix the issue.  

Reasons Why Your Scag Mower Loses Power When Blades Are Engaged

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

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

Tools You May Need for This Job

  • Floor jack
  • Work gloves.
  • Socket wrench
  • Scag blade buddy or C-clamp

Scag Mower Loses Power When Blades Are Engaged: Possible Causes and Fixes

1.   Worn Out Blade Spindle Bearings

Worn-out blade spindle bearings can be a reason why your Scag mower may lose power when blades are engaged. 

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.


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


  • Replace worn-out blade spindle bearings.

2. Dull Blade

If the blades of your Scag mower are dull, it has to work harder to cut the grass and can cause the engine to experience a loss of power when the mower blades are engaged.

It is always important to check the blades and sharpen or replace them when necessary. This will boost the performance of your mowing machine.


  • Check your blades to see if they are dull.


  • Sharpen the blades or replace them if they are in a bad condition.

How To Change Scag Mower Blades

Here are some steps on how to change the blades of your Scag mower: 

Step One: Gather The Required Tools

It is important to get the right tools for your blade removal. Make sure that you have a floor jack to prevent the mower from tipping over.

The floor jack will also lift the mowing machine and make it easy to perform without tipping the equipment and risking oil and gas spillage.

You should also get tools such as a hex set, scag blade buddy or C-clamp and socket wrench.

Step Two: Put The Mowing Machine into Position


Prepare your mower and put it in the correct position to get your work done. Ensure that you raise your mower deck to the highest setting and take off your belt cover.

Make sure that the brakes are engaged and put the floor jack under the equipment. Raise your mowing machine to a high position to ensure a comfortable and easy swapping of the blade.

Ensure that the blades are blocked off to prevent them from spinning during blade removal. 

You can do this by fastening a C-clamp to the deck or making use of a Scag blade buddy to cover the sharp edges of the blade while making contact with the inner part of the cutting deck and also stopping movement.

Step Three: Take Off Blade Hardware and Blades

A series of hex nuts are used to hold each blade in the mower deck in place. These hex nuts are attached to the bolt that goes through the area of the spindle,

Take off the hex nuts so that you can easily remove the blades from the cutting deck. The number of hex nuts depends on the number of blades that your Scag mower uses.

Stroke the bolt through the spindle assembly of the mower. Take off the spacer, bolt and blade. Remove your washer and clear the area so that you can replace the old blade with new mower blades.

Step Four: Install New Scag Mower Blades

Make sure that you follow the procedures mentioned in step two but it should be in reverse order. Replace your washer, and insert your new mower blades and spacer into the spindle.

Use an impact wrench to tighten each hex nut onto the corresponding hex bolt after feeding the bolt through the spindle assembly. 

Make sure that the hardware fixtures are securely fastened before you continue.

Step Five: Prepare Your Mowing Machine For Use

Take off the blade buddy or C-clamp to lower the mowing machine back to the floor. Remove your floor jack and replace any drained fluid(s). 

Reconnect your battery and spark plug cables and your Scag mower is good to go!

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.


  • 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.


  • Replace the clogged muffler for a new one.

4. Clogged Fuel Filter

The function of the fuel filter is to strain the fuel that comes out of the tank to prevent dirt and other contaminants from entering the fuel system.

The mower’s fuel filter can get blocked if it is filtering dirty fuel or it is not changed yearly. This can cause your Scag lawn mower to lose power when the blades are engaged.


  • Check your fuel filter for dirt and other contaminants.


  • Replace the fuel filter with a new one. 

5. Dirty Carburetor

The carburetor makes sure that the correct combination of fuel and air goes into the engine cylinder. This is important for combustion to occur.

The carburetor of your mower can be dirty due to the substances left behind by old gas. 

In this case, it will prevent the carburetor from providing the gas needed to run. This will cause the mower to lose power when the blades are engaged.


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


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

6. Dirty Underside

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

This issue is common with Husqvarna Scag 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.


  • 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.


  • 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.


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


  • 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 Scag mower.


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


  • Replace the pulley if it is sticky or damaged.

9. Dirty Air Filter


The function of the air filter is to protect the engine from foreign particles entering the engine. 

The mower requires air to run properly. If the air filter is clogged or full of debris, it will reduce the performance and engine power.

Furthermore, if the mower does not get the required air, the engine of the mower can become sluggish and may stall. 

It is important to always inspect the condition of your air filter, and clean and replace it when needed.


  • Check the air filter for dirt and debris.


  • Clean or replace the air filter when necessary. 

10. Fouled Spark Plug


A fouled or bad spark plug in your Scag mowing machine can cause an intermittent spark that makes it lose power, affecting the performance of your lawn mower.


  • Check the mower’s spark plug for signs of oil, carbon or dirt build-up on the tip. If the spark plug indicates these signs, it means that you should clean or replace it.


  • Use a wire brush to clean the mower if it is in good condition and it is not very dark in color. You can also replace it if it is in a bad condition. 


It is important to note that this is one of the most common Scag mower problems. Several factors such as a clogged fuel filter, blocked carburetor, worn/loose mower belt, defective spark plug and clogged air filter can cause your Scag mower to lose power when the blades are engaged.

Read our troubleshooting steps and practical fixes in this article to identify and solve the problem.

If you are still experiencing problems after you have checked the above troubleshooting tips listed above, it is advisable to take your Scag mower to an expert for further diagnosis.