Lawn Mower Loses Power When Cutting Thick Grass And Under Load

If you have a really old one, the lawn mower running slow and rough is normal. But you expect smooth operation from a relatively new one.

It’s new but the lawn mower loses power when cutting – indicates some fixable troubles. It happens every now and then throughout the entire life of a mower.

A sudden loss of power while mowing is frustrating and you have to fix it quickly to avoid further damage to your mower. It may lose power for a brief period of time or the power loss may happen for a long time.

The reasons behind the issue are pretty much the same just as it happens when the mower won’t start when hot.

In this article, I will talk about the issue including why the lawn mower bogs down in thick grass and so on. Sit tight and have a cup of coffee!

Why Lawn Mower Loses Power When Cutting?

lawn mower loses power when cutting

You may not face any such trouble while mowing on the level ground, but while mowing on the uphill or slope, it may sputter and sometimes lose power when blades engaged.

So, the cases may vary in some way but the reasons are pretty much the same.

Once you know why this is happening, you can take action to fix the problem. Here are the most common causes and how to fix the power loss issue:

  1. Excessive Dirt

Even if you have a new one, dirt and grass can clog the air filter system or the cooling fins that will lead to power loss. A mower bogs down in thick grass when there is a power loss. The reason is pretty simple.

Due to the lack of enough air and reduced cooling capabilities, the engine will be overheating. So it’s no wonder the mower will bog down under load.

You should check the fuel system as well for excessive dirt and water as well. There will be dirt and water build-up in the carburetor; resulting in poor combustion. Inefficient combustion leads to sputtering and ultimately the engine stops.

Fixing the problem is pretty easy. Clear all the dirt from the cooling fins. Replace old fuel with new oil as well.

  1. Capacity Issue

If you are asking beyond the capacity of the mower, it will bog down. Maybe your hillside lawnmower is capable of mowing on the level ground but you want to cut uphill grass – even the zero turn mower will loose power when blades are engaged.

Or if there is too much weight on it while mowing the uphill grass, the same thing may happen.

Sometimes, it’s just the thick or high grass that may be responsible for the bog down because the mower is not meant for that.

Whatever the reasons, if lawn mower bogging down, lose some weight from it and recheck the capacity of the mower again.

  1. Improper Oil Level

Both the high and low crankcase oil levels will contribute to zero turn mower’s power loss. When the oil level is low there will be less oil to lubricate all the moving parts of the engine.

If it is high, there will be more air in the lubricating system because of the frothy oil. Both scenarios will lead to momentary power loss or prolonged power loss.

  1. Lack of Constant Spark

For so many reasons like carbon, dirt, fuel, oil, etc. the spark plug gets covered over the period of time and can’t spark constantly.

The result is inconsistent ignition and the mower will lose power. If you face any performance issues with your mower, you should immediately check the spark plugs.

You can check and replace a faulty spark plug easily. You can clean it as well.

  1. Dirt & Debris In Blades

When your mower is an old one, the excessive dirt and corrosion can cause sudden power loss when mowing uphill. In can blame the dirt and debris even for the push mower bogging down issue too.

It’s no wonder your mower will work hard when there is buildup like mud and grass coating on the mower’s blades.

For the above reason, your mower will lose power when blades engaged. Luckily, this is something easy to fix. Just remove all the buildups from the blades.

  1. Clogged Muffler

Your mower passes burned gas and other vapors through the muffler. Various liquids and debris can clog the muffler over time.

This is where things get serious. Since no burned gas is going anywhere, your mower will end up having a seized motor.

But how do you know there is a clogged muffler issue?

Well, it’s very easy to look at. If you notice any color smoke coming from the mower, you have a clogged muffler problem.

To stay safe from this problem, just clean the muffler at the beginning of every season.

  1. Dirty Carburetor

This is the most vital component of your zero turn mower and it is solely responsible to supply ignitable fuel to power up the engine.

It mixes the gas with air to create the fuel. But it can’t do so if it is dirty and the seals or gaskets are damaged.

Cleaning the carburetor of the lawn mower and fixing the seals or gaskets can solve the problem. It may not be an easy task since it’s a little bit of a technical issue.

I would recommend hiring a service professional for this issue.

  1. Bad Fuel Quality

The quality of the fuel starts to destabilize after almost 30 days. Since the fuel components start to separate, the quality drops rapidly. When the last time you change the fuel?

When a lawn mower stalls under load, the bad fuel can be the culprit.

Bad fuel will lead to stall out the engine and more so, it will cause other damages to the other components of the mower.


If the engine is relatively new, the above causes may be responsible for the power loss. If it’s beyond that and still the lawn mower loses power when cutting, you should call a professional to solve it.

But before you do so, watch a professional video on fixing a bogged down zero turn mower.

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2 thoughts on “Lawn Mower Loses Power When Cutting Thick Grass And Under Load”

  1. My mower is a Craftsman’s got a Honda engine and just when cutting grass it just it just bogs down I think Dad that the other is there a governor that stops a motor from doing the job when it gets tough

  2. All of these things can have detrimental effects on the fuel injectors, but the number one enemy is definitely carbon build up.

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