How To Clean And Service A Petrol Lawnmower Carburetor

How To Clean And Service A Petrol Lawnmower Carburetor

I often get asked over on my Youtube channel how to clean or service a petrol lawnmower carburettor. In this article, I’m going to show you not just how to service a carburettor but also help you understand how to prevent future problems and where to find parts for your lawnmower.

So, how do you service a petrol lawnmower carburettor? You need to remove the carburettor from the lawnmower and remove the main jet. This often becomes blocked due to stale fuel and water getting into the petrol. Dirt deposits build up in the carburettor and in turn, you don’t get the correct fuel flow to the engine and spark plug.

Why Sevice A Lawnmower Carburetor?

This may sound a little obvious but often I’m asked how to service a lawnmower carburettor when it doesn’t need doing at all, for example when a lawnmower won’t start due to not having any spark or when it,s simply run out of petrol! (believe me, I’ve seen it all!)

If your lawnmower is running fine and not hunting surging or pumping out smoke it will be fine so long as it’s being used regularly and the fuel is relatively new.

You can check out my article on hunting and surging issues here

Check out this playlist from my Youtube channel, there are various types of carburettors covered.

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If your lawnmower starts and dies or starts then stops working when it gets hot or after just a few minutes it could be time to service the carburettor. In this article, I’m going to cover 2 different types of carburettor found on most petrol lawnmower,

You can find lots more information and start repairing lawnmowers for profit by checking out my online training here

Is It Hard To Service A Petrol Lawnmower Carburetor?

Not at all. Of course, everything is a bit awkward and uncomfortable the first time you do it but it’s relatively straightforward and the good news is it’s very similar on every type of lawnmower. If you learn this one repair you can pick up thousands of lawnmowers to repair for-profit and have them running correctly again in under 15 minutes. Plus by the end of this article, you will have all the knowledge you need.

You can find all parts required for your service need in my online parts store here

How Do I Know If My Carburetor Main Jet Is Blocked?

If your lawnmower doesn’t attempt to fire up at all, remove the spark plug and spray some quick start fluid down the spark plug hole. Quickly replace the spark plug and attempt to start the lawnmower. If the lawnmower attempts to start and suddenly dies after a few seconds this tells you have spark but no fuel coming through. This is a good indication that the carburettor needs servicing.

Briggs And Stratton Carburetor Troubleshooting

Let’s use Briggs And Stratton carburettors to start with as an example. Briggs And Stratton generally have two types of carburettors on small engine lawnmowers. The first carburettor is a plastic pulsa prime tank mounted carburettor. This has a primer bulb on the side and it,s very common.

Note If your Briggs and Stratton has a primer bulb on it’s usually this plastic pulsa style carburettor.  

The other style carburettor Briggs And Stratton use, we will cover that later, (It looks more of a bowl shape) but first, let’s take a look at how to service this style of carburettor.

Briggs and Stratton Plastic Pulsa-Prime Tank-Mounted Carburetor Service

This is the easiest type to work on as there are only 2 bolts and one linkage to disconnect then you can remove the entire petrol tank and carburetor from the lawnmower. You will need to remove it completely to be able to service it properly.

Remove the spark plug first. Remove the 13mm bolt to the left of the primer bulb. Take a look at where the petrol tank ends near the front of the lawnmower there is a 10 mm bolt that needs removing. Pull the entire petrol tank towards you and unhook the one linkage near the governor springs. You should now have the entire petrol tank and carburettor off the lawnmower.

Undo the six screws around the carburettor and remove the carburettor. In this type of carburettor, you will find a diaphragm and gasket that sits between the carburettor and the petrol tank. You will need to replace this part if you are having hunting, surging and stalling problems as the little diaphragm supplies the fuel and if it’s wrinkled it will need replacing.

I have done this repair hundreds of times. In fact, this is the most common repair I do as it fixes 90% of Briggs And Stratton running problems.

Turn the carburettor over making sure not to lose the little spring that’s attached. There is a long pick up tube with a filter on the end.

  • Now here’s a killer tip, not many people realize if you pull hard enough this tube comes off.

Pull it off and while wearing safety glasses take a look through it. You should see a little hole with light coming through. Take some carburetor cleaner and spray it on the filter, then blow it out with compressed air. If you don’t have an air compressor you can buy cans of compressed air. Replace the tube by pushing it back on. It will take a bit of force and you will hear a definite click when it snaps back into place.

Take a look at my Youtube video on exactly how to do this repair

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Next, you will see a silver filter on the underside of the carburettor. Slide this off without distorting the shape of the filter. I find twisting it is the best way.

Inside here you will see the main jet. You can remove this by taking a small pick and hooking it out. The holes in the main jet on this model are fairly large and don’t tend to block very often.

I usually leave the main jet in place then spray the whole carburettor with carburettor spray. Next, blow every hole and surface with compressed air and make sure it’s completely dry. Dry the top of the petrol tank off including the hole where the main jet sits. Now replace the diaphragm and gasket, the diaphragm goes on the petrol tank first then the gasket sits on top.

Line the carburettor up with the petrol tank and set everything back neatly. Re-insert the six screws and the service is complete.

Hook the linkage back on the carburettor slide the petrol tank back on making sure the two seal rings are in position on the back of the carburettor, then connect the two bots 13mm and 10mm and the servicing of a Briggs And Stratton pulsa prime tank mounted carburettor is complete and re-fitted.

How To Clean A Carburetor Without Removing It

There are many products available to add to the fuel so you can clean the carburettor without removing it. I have tried lots of these and had very little if any success. If your lawnmower uses a bowl-style carburettor which usually sits behind the air filter box there are a few things you can try. First turn off the fuel if your lawnmower allows, or clamp the fuel line as near to the carburettor as possible. Unscrew the bottom, part of the carburettor and set it aside.

Take a look at this Youtube playlist that covers many areas of carburettor repairs.

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Take a look in the bowl. Safely remove and old fuel and clean the bowl out. On some lawnmowers, you can poke a small piece of wire up the main jet to clear a blockage. In all honesty, this is not the greatest idea but it may be something to try as a quick fix.

Lawnmower Carburetor Location

If you are unsure where your Carburetor is, it’s usually hidden behind a big air filter box. look for a black plastic box with a filter in. The carburetor is usually behind it.

Briggs And Stratton Carburetor Cleaning -Bowl Style

The second type of carburetor that may be fitted to your lawnmower will be a bowl style carburetor. You will find this service procedure is very similar to the Honda Carburetor. The good news is that this style has no diaphragm and gasket but the downside is it’s a little bit more difficult to remove.

Take a photograph of all the linkages and springs that connect to the carburetor before you start. Be sure to take plenty from all different angles. Sometimes trying to remember just won’t do and you will be glad you did!

Remove the air filter cover and air filter. Also, remove the spark plug. You will see two bolts that run through the air filter cover, then through the carburetor and into the engine itself.

Here is an example video of how to do this repair. It’s very similar on may models.

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Close off the fuel line or clamp it as near to the carburettor as possible. Remove the bolts. You will see the carburettor drop down. Again take photographs!

Unhook any linkages and springs and remove the carburettor from the lawnmower. Take a container and sit the carburettor in it upside down until the fuel drains out. Remove the bolt from the bowl and set the bowl aside. You will now need to remove the float and needle. Pull out the retaining pin and remove the float and needle. Be careful not to lose the needle as it likes to go missing!

Next, take a small flathead screwdriver and undo the screw that holds the main jet inside. Visually inspect this part and make sure there is a small hole in it (wear safety glasses) The main jet now usually drops out but, if it doesn’t then take an Allen/hex key and push the main jet down from the top with it.

Clean all the carburettor and bowl with carburettor cleaning spray and blow everything out with an air compressor or a can of compressed air. Re-assemble the carburettor making absolutely certain everything is clean and dry, particularly the tiny holes in the main jet.

Re-assemble the carburettor then connect all linkages and springs and put it back onto the lawnmower. Remember to fit the air filter box, then put the two long bolts through and tighten. This can be a little awkward but just take your time and make everything moves freely on the linkages and springs.

This repair is very similar on lots of petrol lawnmowers including Honda.

You can find lots more information and start repairing lawnmowers for profit by checking out my online training here

Briggs and Stratton Carburetor Rebuild Kit

You can purchase complete carburettors with diaphragm kits to enable you to replace the whole set up rather than service. Find them here

Honda Petrol Lawnmower Carburetor Cleaning

Honda petrol lawnmowers use a very similar set up as the Briggs And Stratton bowl style carburettor. The service is almost identical to the Briggs one which is explained in the previous paragraphs of this article.

Here’s a link to all my Honda lawnmower tutorials

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Different Types Of Lawnmower Carburetor

The good news for anyone wanting to repair lawnmowers for profit is that these two carburettors will be on 90% off lawnmower you pick up to service or repair. More recently Briggs and Stratton have adopted a new plastic bowl style carburettor which is a combination of the two types listed in this article.

Take a look at how to service a new style Briggs and Stratton Carburetor in this article.

Buying Parts

Please take a look at my online store for spare parts

Briggs And Stratton 500 E Carburetor Clean And Service

This is a video of the newer carburettor set up on the Briggs And Stratton 450E and 500E engines.

I have also filmed a full-service video on how to service a Briggs and Stratton 450E 500E Engine here

I really hope this article helps anyone looking to clean and service there petrol lawn mower carburettor. Don’t forget once you learn these simple repairs you can use them time and time again and repair lawnmowers for profit!

You can find lots more information and start repairing lawnmowers for profit by checking out my online training here

Happy Mowing!


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