I’ve always enjoyed using my cordless walk-behind push mower – no pesky cord to haul around and no gas to fill in the tank. But when I need a surge of power to complete larger jobs with ease, my go-to choice undoubtedly is my robust 140cc Briggs & Stratton gas push lawn mower.
The downside however of using a gas-powered lawn mower is maintaining the many different parts like the air filter, spark plugs, hoses, and several other parts under the hood including the lawn mower carburetor.
Of all these aforementioned parts, the lawnmower carburetor is often the most overlooked but is in fact one of the most important parts of a mower just like a lawn mower engine that requires a fair bit of maintenance including annual maintenance.
What is a LawnMower Carburetor?
All gasoline-powered lawnmower engines are fitted with a carburetor. Similar to your car or truck engine, a carburetor helps run the small engine of a push lawn mower, self-propelled lawnmower, or riding lawnmower.
What Does a Lawnmower Carburetor Do?
The only goal of a lawnmower carburetor is to ensure that the right mixture of fuel and air enters the engine cylinder to trigger combustion.
This component of a lawnmower adjusts the balance of air and fuel based on myriad different factors including the amount of time the engine has been running, your speed, and the type of terrain you’re mowing.
Unlike automobile systems, a carburetor of a lawnmower doesn’t contain any throttle butterflies (a pivoting flat valve controlled by the gas pedal) but contains a rubber-type push bulb, through which fuel is primed when the bulb is depressed several times on a push-type lawnmower.
The fuel from the fuel tank flows through the bulb via a hose into the carburetor, which typically allows gas to drip into the carburetor bowl.
The engine creates a suction on the carburetor which mixes the gasoline with air at a specific ratio. After the carburetor has been primed, you can use the pull rope to start the engine.
What Does a Lawnmower Carburetor Look Like?
Most lawnmower carburetors look similar, with a small metal component complete with levers and springs and a distinct bowl shape under the carburetor body.
The carburetor float bowl accommodates the fuel and provides a continuous supply of fuel to the carburetor mixture as required.
The float bowl of a lawnmower carburetor can be drained with either the onsite drain bolt or screw without dismantling the whole system.
Where is the Carburetor on a Lawnmower?
This depends on the type of lawnmower you’re using, whether push, self-propelled, or riding lawnmower.
Where is the Carburetor on a Push Lawnmower?
Just as the name suggests, a push mower is any type of mower that you walk behind and push. The carburetor of a push mower is tucked away neatly behind the air filter at the side of the machine.
If you can locate the air intake filter or air filter of a push lawn mower, you’re one step closer to finding its carburetor. Depending on the machine, the air filter of a push mower is typically encased within a metal or plastic shroud and secured by a screw or with snap fittings.
Where is the Carburetor on a Riding Lawnmower?
The carburetor of a riding lawnmower is located just beneath the hood under the engine blower assembly so you’ll have to undo the hood latches of the engine hood to access it.
Similar to walk-behind mowers, the carburetor of a riding lawnmower is located behind or below the air filter, so once you remove the filter, you can spot it easily.
Signs a Lawnmower Carburetor is Dirty or Damaged
1. Old Gasoline
Old gasoline is the biggest enemy of a lawnmower carburetor regardless of the type of engine whether Briggs Stratton or brands including John Deere.
Your lawnmower will still run on old gasoline but it won’t offer the same top-notch performance that you’re used to.
This is why it’s highly important to empty the lawnmower gas tank when storing the machine for the off-season because old gasoline creates what is known as shellac in the fuel system.
This shellac blocks the inner workings and the air and fuel jets in the carburetor, which further prevents the fuel and air from passing through it.
A clogged gas line can be detrimental to the entire fuel system including the fuel filter, and mower air filter, and may even emit black smoke, which indicates that the machine is “running rich,” or burning too much gasoline.
The only solution for a gummed-up carburetor is a thorough cleaning, which involves removing the carburetor – a task you can do at home rather than visiting a lawn mower engine repair shop.
How to Get Rid of Old Gas in Lawnmower?
Before getting rid of the old gasoline from the lawnmower, check to see if it’s contaminated by pouring some in a glass container, pouring some fresh gasoline in another container, and then comparing them alongside.
If the old gasoline is darker or has a sour smell than the fresh gas, it is probably losing or has lost its efficacy.
Ideally, it’s best to get rid of the old gasoline from the lawnmower completely, but you can try diluting it with fresh gasoline to see if the performance improves.
You can transfer the old gasoline from the machine with a funnel into a jerry can or plastic can jug.
2. Engine Won’t Start
There could be several reasons why your lawnmower engine won’t start, most notably a dirty air filter, loose, dirty, or disconnected spark plug, and/or fuel not reaching the engine, which may be caused by a faulty carburetor or fuel filter.
If you’ve cleaned the air filter and checked that the spark plug and spark plug cable are connected securely, and you’re still facing the issue, making a few adjustments to the carburetor may help.
There may be many issues with the carburetor such as it’s dirty, the diaphragm is cracked or distorted, and/or it’s simply not getting the proper mixture of air and gasoline.
Your lawnmower’s carburetor and engine are protected against debris, dirt, and grass clippings by air filter guards. It is always a good idea to ensure they are clean and in perfect working condition:
- Check and clean the air filters and reinstall them in the machine.
- Next take a look at the vented fuel cap, which is designed to release pressure, allowing fuel to flow from the tank to the carburetor. Remove the gas cap to break the vacuum, then reattach it to see if this resolves the issue.
3. Engine Hunts at Idle or High-Speed
If your mower revs erratically, also dubbed as hunting or surging, the most likely cause is an incorrectly adjusted carburetor.
The good news is that most lawnmowers including John Deere have two screws that allow you to make adjustments to the carburetor yourself.
One screw adjusts the idle mixture while the other controls the idle speed. Since every lawnmower is different, refer to your owner’s manual for the location of the idle adjustment screws, start the mower and allow it to run for roughly 5 minutes, and make the screws looser or tighter until the machine runs and idles smoothly.
4. Lawn Mower Leaking Gas
A lawn mower leaking gas could mean several maintenance issues such as an open carburetor cover, carburetor housing, or carburetor float.
Another reason for carburetor fuel overflow is a stuck carburetor float, which is engineered to regulate the flow of fuel into the carburetor bowl through a simple mechanism.
There are a few potential fixes for this issue including adding a carburetor cleaner to your fuel, tapping the carburetor bowl light with the rear end of a screwdriver, and blowing compressed air through the carburetor bowl drain hole.
5. Engine Lacks Power at High Speed
Apart from old, bad fuel, another reason why the engine of your lawnmower may lack power at high speed is a dirty carburetor. In most cases, cleaning your lawnmower’s carburetor should resolve the issue.
How to Clean Lawn Mower Carburetor?
Experts say that you should check and clean your lawnmower’s carburetor at least a few times a year. The reason for this is simple – as you use your mower, grass, twigs, and other debris can make their way into the lawnmower’s carburetor, and eventually into the engine.
However, your carburetor will suffer breathing issues if the air filter is dirty, so the first thing to do is check the air filter to ensure it is free from any dirt and debris.
How to Find Your Lawmmower’s Carburetor?
Since every lawnmower isn’t built the same, the best way to find your mower’s carburetor is by referring to the user guide that came along with the machine. But here are a few simple steps to locate the carburetor of your lawnmower.
Before getting started, it’s important to ensure that the mower is in a stable position and safe location and will not roll off.
- Place the mower on a flat surface and make sure it is turned off completely. If you’re trying to locate the carburetor of a riding lawnmower, set it in a gear or engage the parking brake just like you would when parking a vehicle on a slope.
- Next, release anything that is making the mower’s internal components inaccessible such as hood latches. Most, if not all push lawn mowers don’t have a hood so can skip this step. This step applies to riding lawnmowers.
- Locate the air intake and the air filter, which are usually found on the side or top of the engine. The air intake and filter are set within a housing, which is either square or round shaped and has slits or holes in the top.
- Detach the filter housing which is attached to the carburetor via latches or screws.
- Locate the fuel line that comes from the gas tank to the carburetor. Undo the small clamp to detach the fuel line from the carburetor.
How to Remove a Lawnmower Carburetor?
To clean a lawnmower carburetor, you’ll have to completely remove it from the machine. You can usually do so with tools such as an adjustable wrench and/or a pair of needle-nose pliers. You may have to remove the engine cover as well depending on your lawn mower model.
- Turn off the fuel valve or make a crimp in the fuel line, and remove it from the carburetor. A little fuel may spill out at this time so you should dress appropriately for the job.
- Detach the choke and throttle linkages from the carburetor throttle lever, and remove the carburetor from the mounting bolts using a sliding motion.
- Unthread the screw to remove the carburetor bowl.
- Release the float pin and carburetor inlet needle.
How to Clean a Lawnmower Carburetor?
Once you’ve removed the carburetor from the lawnmower, you can use a carburetor cleaner to remove grime and fuel, and a dry rag to clean the external parts of the carburetor.
If you notice any signs of rust, get rid of them with sandpaper or a rust remover. Allow all the parts to dry and reinstall them and the carburetor back on the lawn mower.
If your carburetor is showing signs of physical damage, you may have to replace it with a new one instead of reinstalling the old one back on the machine.
How to Clean Lawn Mower Air Filter?
If you keep your lawnmower’s air filter clean, you will have less dirt and debris getting into the carburetor.
Your lawn mower’s air filter is in fact the first line of defense against dirt and debris that stems from the mowing process and prevents dirt from entering the engine via the carburetor.
It’s a good practice to clean your lawn mower’s air filter every 25 working hours or whenever you notice a dip in performance. Replace the air filter if damaged or after 300 hours of operation.
- Shut down the mower before getting started with the cleaning process, and make sure all the parts have come to a complete stop and have cooled down. Note: You should never operate a mower without an air filter as doing so will cause serious damage to the machine and yourself.
- Disconnect the spark plug wire and remove the protective screw that secures the mower’s shroud (covering) over the air filter. The exact location of the air filter could vary by model but most commonly is located near the top of the engine, and is protected by a shroud.
- Remove the air filter and take a closer look at it. Your lawnmower could be fitted with one of three different types of air filters:
- Foam air filter
- Paper air filter
- Dual-element air filter.
If you have a paper air filter, gently tap it on a flat surface to knock off any loose dirt and debris. Next, hold it up to a bright light source and if the paper blocks a considerable amount of light, then it’s time to replace it but don’t try and clean it further.
A foam lawn mower air filter should be replaced if there are any signs of crumbling or visible brown or yellow staining. If it’s in good condition, you can go ahead and clean it.
For a hybrid air filter, refer to the manufacturers cleaning guidelines. But usually needs to be replaced if it’s become stiff, brittle, or significantly stained.
Cleaning a Lawnmower’s Foam Air Filter:
- Washing: You can wash your lawnmower’s foam filter in the wash sink or with a garden hose to get rid of stubborn dirt. If it’s extremely dirty, use dish detergent to remove the dirt but be sure to rinse the soap out thoroughly.
- Drying: Let the filter air dry under the sun, after which you can oil it. You can apply oil with your hands or directly pour it over the foam filter. But don’t get carried away as you don’t want the oil dripping into the mower.
- Re-installing: Before reinstalling the air filter, clean the housing and the shroud with a dry cloth and not with a compressor because it could force dirt and debris into the carburetor and engine. Reinsert the air filter and make sure it fits snuggly into its dedicated slot. Lastly, replace the shroud but be careful not to tear the filter. Don’t forget to reconnect the spark plug, so you can start your lawnmower.
How to Perform Lawn Mower Maintenance?
Maintaining your lawn mower will improve both its performance and service life. Lawnmower maintenance can be carried out at any time of year but the two best times are before the first mow of the season and at the end of the season when it’s time to retire the mower.
Many people choose to take their mower to a professional repair shop for maintenance but these simple checks and fixes can be performed in the comfort of your home.
Since every lawnmower model is different than the other, it’s best to refer to your owner’s manual for maintenance instructions but here are some common tips to keep your mower in tip-top shape.
1. Replace the spark plug
Removing the spark plug ensures that the mower doesn’t accidentally start. A lawnmower spark plug should be changed every mowing season, after 25 hours of use, or if the mower won’t start.
- Start by disconnecting the spark plug lead.
- Clean the area to prevent any debris from seeping into the combustion chamber when you remove the plug.
- Use an appropriate spark plug socket to remove the spark plug.
- If there are any light deposits on the plug, clean them with a soft cloth.
- Replace the plug if there are any damaged electrodes.
2. Change the oil
You should ideally change the oil in your mower every 50 hours of operation or after every mowing season. Most mowers come with a drain plug that allows you to drain the oil from the mower. If your mower didn’t come with a drain plug, simply flip the mower over on its side and allow it to drain via its fill hole.
Make sure to replace the oil with the right type of lawnmower oil, but 10W30 is the grade suitable for most lawnmowers.
3. Drain the fuel tank
If your lawnmower won’t start, the common culprit is old gas. Lawnmower gas can go stale and lose its volatility in as little as 30 days and leaving gas in the tank when not in use can eventually corrode the fuel tank.
Remember to drain the fuel tank at the end of each season and refill it in the spring, and take all the necessary precautions while performing this task.
4. Clean the mowing deck
The mowing deck is perhaps the most used component of a mower but is also the most overlooked when it comes to cleaning and maintenance.
It’s a good practice to clean the mowing deck every time you finish cutting the lawn. Dirt, cut grass, and debris can accumulate onto the area above the blades, aka the mowing deck, and once it dries, becomes incredibly hard and difficult to remove.
You should perform a thorough mower deck cleaning at the end of the growing season, which entails removing the spark plug and cleaning the mowing deck and blades thoroughly.
5. Check the tires
Regardless of the type of mower, whether walk-behind mowers or riding lawn mowers, it’s important to check the tires to ensure they’re in good condition and are free from chips and damage.
Here’s an informative video on how to remove a lawnmower carburetor and the steps to maintain and repair a lawn mower:
A lawn mower’s carburetor is easy to find, just locate the air filter and it should be right behind it. Both the air filter and carburetor of a lawn mower require regular cleaning and maintenance or else can cause several performance-related issues and in worse cases may even affect the service life of the mower.
Hi, Alex Kuritz here. Growing up I remember that my family had one of the best lawns in the neighborhood. Richly green and lush. I did a lot as I grew up in terms of caring and tending for not only my family’s lawn but also my neighbors. I can say I have years of experience, and I am here to share it with you.