How to Fix Surging Lawn Mower

Do you have a mower that surges when it’s running? There are many possible reasons for this, but most of them can be fixed with some simple adjustments. To restore the problem, you need to make sure your blades are in good shape and clean; they should be sharpened regularly.

You’ll also want to check how tight the blade bolt is on your mowing deck (it needs to be adequately tightened!) And if none of these things work, then chances are it might just be time for a new lawnmower! In this blog post, we will cover how to fix surging lawn mower so that you can make it quick work out of cutting grass and getting rid of weeds without all that bending over.

How to Fix Surging Lawn Mower

10 Reasons Why Your Lawn Mower Surges When Running

1. Dirty Air Filter:

This is the most common reason for a lawnmower that surges. If your lawnmower is equipped with an air filter, you should clean or replace it often, depending on how often you use your mower. A dirty air filter will cause the engine to work harder, increasing fuel usage and producing more emissions.

2. Obstructed Carburetor:

If your lawnmower suffers from the symptoms of surging, it may be a result of a dirty or clogged fuel line

3. Dirty/clogged Spark Plug:

If your engine is not firing on all cylinders, it may be due to a dirty spark plug. This can also increase fuel usage and prevent proper combustion. A clean spark plug is essential for optimum engine performance and fuel efficiency.

4. Clogged Air Filter:

A clogged air filter restricts airflow and increases your engine’s workload. Clean or replace your air filter as needed to prevent this issue from occurring.

5. Incorrect Fuel/oil Ratio:

If your lawnmower is not getting the correct amount of oil, you will use excess fuel, and this will cause it to surge. Make sure that you check your owner’s manual for proper engine oil dosage.

6. Overheating:

Your lawnmower will surge if your engine is overheated due to a lack of water or overheating. This is because an overheated engine reduces its power output, which causes it to work harder.

7. Dirty Muffler:

If your lawnmower is equipped with a muffler, check if it’s clean or replaces it as needed. A dirty muffler will create excess heat, and this will cause your engine to work harder and surge.

Using Dirty Muffler

8. Incorrectly Gapped Spark Plug:

A spark plug with an incorrect gap will cause your engine to surge and increase fuel consumption. Make sure that you check your owner’s manual for the recommended gap of your mower.

9. Leaking Oil:

If there is a leak in the crankcase, it could be caused by a worn-out piston ring. Also, if your mower has an oil-drip hole, make sure that it’s clean and free of debris.

10. Engine Speed Too Low:

If the engine speed matches the speed of your lawnmower, it will cause your mower to surge. This is because if you exceed its limits, the engine cannot handle the extra work, and this causes it to work harder. So, for example, if your mower’s max engine rpm is 3600rpm and you are running at 1800, it will cause it to surge.

You Can Check It Out to Install Side Discharge on Lawn Mower

6 Methods on How to Fix Surging Lawn Mower:

1. Clean Air Filter:

If your lawnmower has an air filter, you can clean or replace it as needed. However, if it’s dirty, which is the most common reason for a mower that surges, your engine will work harder and faster than it needs to. This will cause it to surge and can shorten the life of your mower’s engine, so clean or replace as often as necessary.

2. Check Spark Plug:

If the spark plug is dirty or damaged, it can affect how well your mower starts and runs. Clean the plug using a wire brush and feel to see if it’s hot. If so, an air leak may be caused by damage or poor connection. Next, look around the base of your lawnmower to find where you can access and tighten or replace the spark plug. If the air leak is small, you may be able to pull it yourself. If not, you’ll need to take it in for service.

3. Change the Oil:

If your mower isn’t running on clean oil, your engine will work harder, so change or clean it often. Check your owner’s manual to find the right amount for your lawnmower. Remove the dipstick, wipe it on some newspaper to dry it off, and then replace it. Pull it back out and look at how many inches of oil are present in your mower’s engine. If you don’t have enough oil, add more before restarting.

4. Add Fuel Stabilizer:

Stabilizing your lawnmower’s fuel before storage will keep it from deteriorating. This is better than just running the mower until it runs out of gas because that could leave you with a carburetor full of stale gas that won’t run properly when you restart in warmer weather. So instead, add a stabilizer to the mower’s fuel tank and allow it to run until the engine stops.

5. Replace Fuel Filter:

If the fuel filter is dirty, it could also cause surging. It should only need to be replaced every few years or so, but you can return it whenever you use a stabilizer in your mower’s gas tank. If a fuel filter is clogged and isn’t being cleaned regularly, it will allow particles into your engine that can damage it and even break it.

Using Replace Fuel Filter

6. Check and Tighten Bolts:

A lawnmower that surges can also result from a loose part, like a bolt or hose clamp. You’ll need to check your owner’s manual for where you can access all of these parts, as not all models are built alike. Tighten as required and check for signs of damage. If the piece is damaged, replace it with a new one from your lawn mower’s manufacturer.

How Do You Stop a Lawn Mower From Surging?

If you’re experiencing surging with your lawn mower, there are several steps you can take to solve the problem. Start by cleaning or replacing the air filter. A dirty air filter can prevent the engine from getting enough air, which can cause it to surge.

It’s also important to check the fuel system for clogs in the fuel filter or fuel line, as this can also cause surging. If the fuel system is clean, you may need to adjust the carburetor to the manufacturer’s specifications. Finally, check the spark plug and inspect the blade. A damaged or unbalanced blade can cause surging, while an old or dirty spark plug can also be at fault. Following these steps, you can stop your lawn mower from surging and return to a smooth mowing experience.


This article is going to cover how to fix a surging lawn mower. It has also provided helpful information on what causes the problem and ways of solving it.  Surging occurs when the engine speed fluctuates widely, often as much as 1,000 rpm at times or more than 5% from its average running rate.

The oscillations are usually caused by one cylinder firing before another fully completes its cycle. All of the information in this blog should have helped you understand how to troubleshoot your lawnmower. If not, let us know, and we’ll be happy to help!

Jennifer Branett
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