How To Clean Carburetor On Lawn Mower Save Money on Repairs

How To Clean Carburetor On Lawn Mower

When you want to start mowing but your 4-stroke lawn mower won’t start, the  problem is probably the carburetor.

That’s why it is very important that if you have a lawn and want to maintain its beauty, you should know how to clean carburetor on your lawn mower.

How To Clean Carburetor On Lawn Mower

Why Problem Arise With A Lawn Mowers Carburetor

The function of carburetor especially for the 4-stroke engines like the lawn mowers is to mix the air and gasoline in exact proportion so that when this enters the combustion chamber of your engine, this can be easily combusted with the help of the spark plug.

But when the carburetor has an issue, either you will have a flooded lawn mower that won’t start or a stalling lawn mower that let you start the engine but then dies.

There are many causes why carburetors fail

Clogged carburetor 
This is the number one problem that is attributed to the carburetor becoming clogged with dirt.

This dirt may come from old gasoline that has gummed up over time inside the gas tank and carburetor.

It could also come from rusts or corrosion or sometimes there is dirt that comes through the air filter and into the carburetor and cause clogging.

A carburetor has many small components: floater, main jet, fuel bowl, fuel bowl nut, needle, idle pin, choke pin and hinge.

If any of these got clogged up with dirt or rust, the carburetor will fail and ultimately cause flooding.

Defective spark plug

The role of the spark plug is to produce electricity in between its electrodes and the spark will ignite the mixture of air and fuel in the combustion chamber and create combustion.

This enables the piston turn the crankshaft.

If the spark plug is defective or flooded with gasoline due to constant throttling of the engine, the spark that it will produce will not be enough to ignite the fuel mixture.

In this case, some of the mixtures may revert to the carburetor and mix again with the gasoline.

Eventually, this can cause choking of the engine and flooding within the carburetor.

Flooding due to dirt on the needle valve
The needle valve is part of the float that controls the entrance of the gasoline.

When the float rises, the needle valve will press on the needle seat to stop the gas flow once the right level of gasoline is reached.

However, when this seat is plugged with dirt, the flow of gas will be uncontrolled and flooding will result.

needle valve

Defective float
The float is one of the carburetor parts responsible for controlling the flow of fuel inside the carburetor.

As it floats on the fuel, it presses the needle valve and blocks the needle seat where the fuel passes through.

If the floats develop a crack, it won’t float efficiently thus the flow of gasoline in the carburetor will not be efficient and flooding can also occur.


Dirt on the nut/screw on the carburetor’s fuel bowl
This is also one of the most common problems that can cause flooding in the carburetor due to the blocked hole on the nut screw that supports the fuel bowl.

The fuel bowl is where the fuel is stored until it will be pulled upward and mixes with the air in the combustion chamber.

When the fuel bowl nut screw hole is blocked with dirt, the combustion chamber loses its ability to suck up the fuel because of the vacuum that’s holding down the fuel.

Eventually, the continuous flow of fuel will also result in flooding.

As you can see, flooding is one of the major problems of the carburetor that is caused mainly by dirt.

This is why if you familiarize yourself on how to clean a lawn mower carburetor because if you take your machine to a repair shop,

you have to shell out a small fortune for fixing it, which in reality can be simply done by you.

But how would you know that the carburetor is the one causing the problem?

It’s through obvious symptoms.

The following signs will tell you that you have a dirty and clogged carburetor.

Symptoms Of A Dirty Lawn Mower Carburetor

1. It would not start.

This is mainly due to debris that got stuck in the needle valve which stops it from closing.

And as the gas continues to drip down the carburetor bowl, overflow can result which we call flooding.

The result of fuel overflow could also inter the spark plugs chamber thus your machine will experience hard start-up.

2. Mower starts then dies.

Whenever you start the engine but won’t run for any length of time, the cause can be due to a dirty carburetor.

When there is the accumulation of dirt inside the carburetor,

the mixture of gas and air that the engine requires to do complete combustion cannot travel freely to the internal combustion chamber and therefore your mower will not start or keep going and eventually dies.

3. Running lean symptoms.

When there is the imbalance mixture of gas and air, there could be the popping or sneezing sound that you will hear in the intake.

This is due to the wrong air and fuel combination which must either be 12:1 or 15:1 air to fuel ratio.

 Dirt somewhere is what can cause failure of the carburetor to do the proper mixing of air and fuel.

Running lean means the oxygen is likely to go over the right proportion compared to the proportion of the fuel.

That’s why once the wrong fuel mixture enters the combustion chamber this causes small blasts and therefore the popping sounds.

4. Running rich symptoms.

This is exactly the opposite of running lean which means the proportion of fuel is in excess while the air proportion is insufficient based on the air to fuel ratio and the culprit is also a blocked part inside the carburetor.

Black smoke from the exhaust is a strong sign of a running rich problem.

Now, the only solution to solve the problem of a dirty carburetor is by pulling it apart and cleaning it.

If you do not know how to clean carburetor on lawn mower, the following procedures will make this easy for you.

Steps-By-Step Guide Cleaning your lawn mowers Carburetor

Things you need 

Carburetor cleaner, ratchet with the right plug size, toothbrush for cleaning up rust and corrosions, air compressor gun, clean cloth, small basin with engine cleaner, screwdriver and a carburetor kit just to be sure you have replacements for the gaskets.

1. Disconnect the spark plug cap and pull out the air filter along with its case.

Check for signs of wearing of the air filter including the gaskets that is between the air inlet and the carburetor.

2. Unplug the spark plug and clean the spark plug chamber by inserting a clean cloth and twisting it inside.

If you only want to clean the spark plug like from carbon deposits, spray it with a carburetor cleaner or an engine cleaner and brush the dirt off with a toothbrush and dry it using a clean cloth.

Replace the spark plug if you think its faulty.

3. Disconnect the fuel line using a needle nose plier and drain the gas from the tank completely through the fuel line.

4. Disconnect the throttle and idle lines by pulling them out carefully from the carburetor.

5. Carefully detach the carburetor and prepare a small basin filled with an engine cleaner solution.

This is where you’ll put all the screws, pins and hinges you will be taking out from the carburetor.

6. Under the carburetor is the fuel bowl that is being supported by a screw with a hole.

Take these out and put it them in the basin.

7. Detach the floater by unscrewing its hinge and also unscrew the needle valve attached to the floater.

Then go on unscrewing the main jet screw, idle screw, pilot jet from the carburetor block and put them all in the basin including the floater to loosen up dirt.

Reminder: Before taking out the idle screw, count first the number of ridges on the screw that went through the hole on the carburetor block.

This will help you remember how deep the screw should go once you screw it back.

7. Check the floater for any cracks or holes. A damaged floater will not float efficiently and will cause flooding on the fuel bowl.

Change it if it has cracks or holes.

If it is dirty, spray it with a carburetor cleaner and brush it using a hard toothbrush and put it along with the screws in the basin for further cleaning.

8. Blast every hole and port you see on the carburetor block with carburetor cleaner using its straw and let the liquid drip from the other side.

Use compress air to blow up the liquid along with the dirt. Spray once more and use compress air again.

Don’t use metal wire in cleaning the ports where the screws are attached to avoid damaging the gaskets inside them.

9. Go back to cleaning the screws. Clean every piece of them by spraying them with carburetor cleaner and inserting the carburetor cleaner’s straw in their holes and blasting it to clear up clogged dirt.

Don’t forget to spray also the hole in the screw that supports the fuel bowl.

10. After cleaning out all the screws including the floater, lay them all on a clean white cloth to avoid losing them while drying them.

11. Check all the gaskets you find on the carburetor and replace them with new ones from your carburetor repair kit including the gasket on the air inlet.

If you don’t have a carburetor repair kit, you can buy a “gasket maker”. This is a liquid silicone you can apply and become hard like rubber when it dries.

12. When everything is cleaned up and every hole is cleared and dried, put everything back in their place including the floater reassemble parts in the reverse order.

13. Reattach the carburetor including the throttle and idle lines and reconnect the fuel line.

14. Put back the clean air filter or better yet install a new one.

15. Put in some gas on the tank but don’t fill it up yet.

16. Recap the spark plug and start the engine while the choke is on.

Once the engine starts, immediately turn off the choke and let the engine run for five minutes to the let the oil circulate and heat up the engine.


Now that you know how to clean carburetor on your lawn mower, the next time your carburetor gets dirty you definitely know how to clean it.

If you have a reliable carburetor cleaner product with you carburetor, cleaning would be very much easy.

You can try loosening first the fuel bowl that’s under the carburetor,

draining and cleaning the bowl and blasting the hole in the screw with a carburetor cleaner,

reattach them and then try restarting your lawn mower.

This usually works.

One more thing, make sure you have an efficient air filter for a replacement because if your machine’s air filter is not doing its job efficiently,

the air intake issue can also cause a problem with your carburetor and not totally the dirt problem.

Leave a Comment

Your email address will not be published.