[Fixed] Lawn Mower Won’t Start After Cleaning Carburetor

Most of the time, lawnmowers don’t get started because the carburetor is clogged. But chances are you’ve cleaned the carburetor in the right way, yet you’re struggling with starting the mower. 

So, why your lawn mower won’t start after cleaning carburetor? What’s causing the engine not to start or stop after getting started?

Well, too many questions. Relax for a second. We will give every necessary answer to the questions with explanations. 

Let’s get started. 

How Do Carburetors Work On Lawn Mowers?

We get how it does feel when a lawnmower doesn’t start even after you clean the carburetor and we’ll proceed with the solutions later. 

But before doing so, you should understand exactly what your carburetor’s job is. It will help you to keep the carburetor in good working order. 

Actually, to start your lawnmower engine, it’s important to produce enough heat in the first place. It’s crucial to minimize fuel consumption and maximize the power of your engine. And, carburetors combine the air and fuel in the right proportion and let the engine start.

Since the carburetor is the core part (it dominates the engine directly), you may face trouble starting the engine when the carburetor doesn’t work.   

And, most of the starting-related issues happen because of a dirty, damaged, or faulty carburetor. So, you must take care of the part of your mower to get the most use of the mower.   

Why Lawn Mower Won’t Start After Cleaning Carburetor- How to Fix?

You’ve cleaned the carburetor, but the mower still won’t start. Then there are other parts you should check to understand who’s the culprit here. 

Dirty Air Filter

Air filter removes grass, grit, and dust from the main airstream so that the fresh air can enter the engine. So, basically, it cleans and filters the incoming air of dust and debris. Otherwise, the important parts of your engine can be damaged. 

But sometimes, the air filter can be clogged with dirt and debris. If it happens, the carburetor can’t get the proper amount of air for creating a perfect mixture so that your engine can run on. 

So, you must be sure that the air filter isn’t clogged or damaged. The thing is, the air filter can be dirty over time and it’s natural. But you should clean it regularly and replace it when it’s needed. 

Now, let’s see how to clean the air filter of your lawnmower

Start with removing the air filter. Then, use the palm of your hand for dislodging debris like leaves or grass clippings. Now, you can use soapy water to wash foam filters. Now, things should be just fine. However, if they’re not, maybe it’s time to replace the air filter.  

Dirty Spark Plug

If you’ve cleaned the air filter as well but still the lawn mower isn’t getting started, then give your attention to the spark plug. If the spark plug is wet, dirty, or faulty, the engine won’t start. So, let’s see how you can deal with it. 

First thing first, remove the spark plug and inspect its condition. To check for spark, consider using a spark-plug tester. You’re supposed to see a blue, strong plug. Things are easier when you test this in a darkened garage. 

If you see a weak spark or simply no spark, then you should replace the plug.

And, about a wet spark plug, it’s even the worst case because it happens due to oil leaking into the combustion chamber. If this is the case, it’s better to take your mower to the servicing or reinstall the plug. 

The spark plug should never appear burned or oily. So, replace the plug whenever you face these situations. 

Broken Flywheel Key

Did your engine get hit by obstacles like rocks? This type of circumstance can kill the engine. Maybe your carburetor is clean and other parts are also checked and fine but still, the engine isn’t getting started. 

Then, chances are you’ve somehow broken the flywheel key. The flywheel key is nothing but a small metal piece that lines up the flywheel ideally and sets the perfect engine timing. When the engine gets hit by an obstacle, it stops the mower blade but the flywheel continues spinning. 

 If this is what happens here, the engine timing will remain off and your lawnmower won’t start. And, things will be okay only when you replace the flywheel key. However, it’s not something hard to deal with. 

Check whether you do have a gear puller set in your garage and that’s all you’ll be needing to replace the flywheel key.   

Carburetor Isn’t Tightly Bolted or Screwed to The Engine

This may sound petty but this simple issue can prevent your lawnmower engine from getting started. 

The carburetor is supposed to make an ideal seal with the engine. And it’s possible when the carburetor is tightly screwed. Moreover, any o-rings or gaskets shouldn’t be damaged or worn. 

Water in The Trank

Another reason why the engine won’t start at all or stall is water in the gas tank. Remember whether you left the mower exposed for a long time or all winter because it can lead water to leak into the tank cap. 

If you left gas in the tank for the whole winter, chances are there was an unexpected accumulation of moisture. The possibility is bigger when you use ethanol-related fuel. It’s because ethanol can attract moisture and only 3-4 tablespoons can cause difficulty starting.

So, when there’s water in the tank, you should drain the gas tank. To do so, take a damp cloth or sponge and fix it onto one end of a long screwdriver. Then, soak up the remaining water. If the problem doesn’t go away yet because there’s a lot of water, then do something else. 

Take off the float bowl and then drain the residue of the bowl as well as the fuel tank.   

Old Fuel

Yes, sometimes, it can be the old fuel that’s making your lawnmower starting difficult. When the fuel evaporates, chances are there will be a deposit of gel, gum, or varnish. As a result, the moving parts of your lawnmower engine may be clogged. 

So, the gasoline in the tank must be fresh. In this case, you can purchase a gas stabilization product that will store the oil fresh for longer. This reduces oxidation and helps greatly in preventing fuel degradation. 

Tips to Maintain Your Lawn Mower Carburetor

I’m sure that you prefer sealing the chances of happening all of the problems in the first place rather than dealing with them later. So, here are some helpful tips to keep the carburetor in working order. 

  • Use a quality gasoline stabilizer that keeps the fuel fresh for up to 12 months.
  • Always check the air filter, fuel filter, fuel line, and other related parts to make sure that any of them isn’t clogged.
  • Replace the carburetor if you see it starts corroding.
  • Make sure the engine is getting enough fuel and air.
  • The battery should be fully charged.
  • The carburetor isn’t flooded. 

Frequently Asked Questions (FAQs)

Why does my lawnmower start and then stop?

Maybe your mower has run out of fuel. Give a few tries and check whether you have a spark. Also, water or dirt in the float bowl also causes the engine to sputter and your mower may stop. Another problem can be there, when the ignition coil fails, your engine may stop all of a sudden. If this happens, replace the coil. 

How do I know if my lawnmower carburetor is bad?

The most common problem people face is the engine has trouble starting. Sometimes, the engine may start but stalls after a few minutes. 

What causes a lawnmower carburetor to go bad?

Dirt and debris can clog the carburetor or other parts close to the carburetor. This is the most common reason why your carburetor goes bad. Also, rust can be a villain, so make sure you check the parts regularly. 

Do vinegar or baking soda work well for cleaning carburetors?

Yes, these natural ingredients work great to clean carburetors. 


By now, you know why your lawn mower won’t start after cleaning carburetor and how you can fix it. 

You also may understand now how important it is to properly clean the carburetor and other parts of the mower. Perfect maintenance can save your mower from being damaged soon and provide you the most advantage. 

Apart from the carburetor-related issues, other problems may also be clear to you now. Take care of the mower and have a longer journey with the machine. 


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