How To Tell If Lawn Mower Carburetor Is Bad? Find Out Here

Written By James
Updated May 8, 2022 by James

How To Tell If Lawn Mower Carburetor Is Bad? Find Out Here

Engine carburetors are the heart of any engine, and this is especially true for smaller engines such as those in a lawn mower. Without proper maintenance or care, even the most balanced caburetor will gradually beging to decline and show fault. Usually, preventing a lawn mower from starting or working efficiently.

How to tell if a lawn mower carburetor is bad? These are several signs, the most common being a lawn mower failing to start, although this can also be cause by other problems with the mower. Popping noises during the intake, thick black smoke leaving the exhaust, and even wet spark plugs are also signs of a fault with your small carburetor.

Lawn mowers, snow blowers, and most smaller four stroke engines rely on the carburetor, so knowing how to spot a fault and fix it can be a handy skill. Replacing a carburetor can be expensive however, so maintenance is just as important. 

The most basic method to maintain the equipment would be regular cleaning, but any number of carburetor issues could plague your mower. If you want to take steps to fixing and avoiding future problems, then read below to learn how to maintain a clean carburetor.

What is a Carburetor?

A carburetor is the main component of a small engine, allowing the whole thing to function. Without it, your lawn mower would not run. The carburetor is the main catalyst for combustion, which drives any and all engines, whether that be in a lawn mower or an SUV.

Since it is at the centre of everything, it's only natural that carburetor contamination occurs. Overworked by pumping fuel and driving your small motor, sticky residue and rust can quickly lead to issues with your major carburetor components. 

You can find a small engine carburetor in all your average fuel powered mowing equipment. You could use this guide to repair a hand pushed lawn mower that is gas fed, or for full ridden tractor mower carburetor repair. 

How Does it Work?

A carburetor is a feat of modern engineering, and works by being both responsible for initial combustion and maintaining it. A carburetor inlet needle permits the flow of fuel into the engine, where a float pin then maintains the level of appropriate fuel intake. 

Other parts of the mower help the fuel pump, but the carburetor uses a fuel filter inlet and air filter housing to maintain a delicate balance of air and fuel in the engine. This is the same in all lawn mower fuel systems, and helps promote efficient gas consumption and prevent the toxic smoke you might see leaving a car exhaust.

Signs Your Carburetor Needs Cleaning

If your engine fails to start, then you may need to inspect your carburetor. This is most likely an issue with your fuel filter, which prevents proper carburetor intake. This means the appropriate ratio of fuel and air can't reach where they need, and causes a fault in the mower.

It should be noted that this is not always an issue with engine carburetors. A non-starting engine could be the result of any number of issues relating to the engine's components, as small engine are engineered in a very particular way. This means any disruption to the system can cause issues, although a carburetor and the fuel filter should be your first checks on the list.

Flooding and debris can also cause a balanced carburetor to be thrown off. This usually leads to a fuel overflow, since it prevents the carburetor needle valve from fully closing. As such a dirty carburetor gas bowl will result in overflow, typically resulting in a wet spark plug. 

A soaked spark plug will not spark for obvious reasons, which then prevents ignition. As such, keeping yhe lawn mower's fuel bowl gaskets clean is a top priority for mower maintenance. So before you try anything else, take some time to clean your carburetor bowl. If flooding continues, you may have a weak carburetor float needle, which will need replacing. 

Problems with a Started Mower

A typical carburetor can still face problems, even if the engine manages to start. Fuel flows, but not necessarily in the correct manner, leading to a "lean" or "rich" engine. Even if the fuel valve closes, and you overcome a slow fuel flow, these problems can endure in your mower. 

If your engine is running "lean" then it is an indication that your mower air to fuel ratio has been disrupted. Too much air or not enough fuel leads to popping noises, as if the engine is stuttering. A problem with your fuel supply or other fuel system faults can lead to an inefficient mower thanks to a lean engine.

A "rich" engine on the other hand has the exact opposite issue. Not enough air or too much fuel, noticeable from black smoke leaving the exhaust or an obvious increase in fuel consumption while mowing. Bad fuel that is old, or even a mixture of fuel (namely ethanol fuel which mixes regular automobile gasoline) can lead to a rich engine, as well as residue and debris.

If you have any doubts about fuel quality in your mower that concern you, be sure to drain your fuel tank and refill it with fresh fuel. A restricted carburetor can be easy to spot and fix, but further issues caused down the line by improper fuels can stack up fast. 

A fuel stabilizer can also be added to your tank in a pinch, if you find yourself unable to correctly drain and replace the fuel inside your lawn mower. This is not a be all and end all fix, although it is still better than relying on faulty fuel and gas for running your engine and ruining your gardening experience. 

Signs Your Carburetor Needs Replacing

In a worst case scenario, you may have to replace your carburetor. In this event, you can usually find for anywhere between £25 and £75. This is obviously a last resort measure, but it's possible that a carburetor may not be fixed after a deep clean, and may ultimately need replacing. 

So how do you tell if you have a dead carburetor in your mower? The most drastic sign would be a corroded lawn mower carburetor. Corrosion is a sign of an unfixable problem, and you are unlikely to start your mower properly with a damage core such as this. 

Certain components of the machine may also be broken. If you find a carburetor inlet needle, which will prevent the fuel filter getting gasoline, stuck and unmovable then you may have to face complete carburetor removal. Every piece, from the carburetor throttle lever to the carburetor jet, is important for correct function. 

These different parts may be trickier to replace than a full carburetor. So unless you want to find out your carburetor bowl type, or which carburetor bolts you need specifically, you may be better off just removing the whole thing and installing a fresh one. 

How to Clean your Carburetor

You can find dedicated carburetor cleaners online and in stores commonly. Uninstalling and maintaining a quality carb only requires basic tools, although proper engine repair tools are also usable. Spray carburetor cleaner on a removed product for best results, removing debris and other residues.

A number of "home cures" are available as well. The most common being a kitchen fix, where you boil the carburetor in vinegar for half an hour. You can also find a carburetor repair kit, designed to help you remove carburetor fasteners for a deeper clean. 

Since different types of blockages, gumming, and damage can be found in a carburetor, you may be able to save some time by only cleaning the specific components. If you have issues with flooding and fuel overflow, for example, you can simply clean the spark plug with carburetor cleaner rather than spending time performing a major deep clean.

Of course, this may not always be the case. A deep clean is more preferable in most cases, but if you're on a budget for time or trying to make your carburetor cleaner and kits go the distance, specialised maintenance is an available option. 

Being a delicate piece of equipment, it is more reccomended that carburetor kits are used over DIY home fixes, to avoid unresolvable damage to the equipment. Damage to more advanced equipment such as the fuel solenoid, an electromagnetic valve that opens when the mower starts to allow fuel flow, will more than likely lead to a full carburetor replacement. 

When removing a carburetor, you should always make sure to take note of the gasket locations, and orientation of other key parts. This way, you can refit the carburetor more easily, and are less likely to discover any faults upon reinstallation. An improper refit will make itself very obvious when you start the engine once again. 

Other Parts That May Cause Issue

The fuel solenoid needs to function in order for your mower to really work. Without the fuel solenoid, you can expect to face flooding problems, or even a total lack of fuel flow in your engine. Fuel lines are just as important as a functioning carburetor, so make sure everything is in top working order.

Every lawn mower has a fuel pump, dedicated to getting the petrol or gasoline where it is needed. Engine repair tools are essential if you ever find yourself working on the lines in your mower, as they can be more complicated than some of the other equipment.

The Small Things

Being at the heart puts a carburetor under constant work and stress. Fuel residue, debris, and damage to equipment are a common carb killer. No amount of engine repair tools can fix permanently damage equipment, they can only replace them. 

Although larger components such as a fuel tap, fuel tank, and the aforementioned fuel solenoid can cause problems, basic fittings also need to be routinely checked. A loose fuel bowl bolt can be disastorous, a missing carburetor bowl nut can cause serious damage, so make sure everything is fitted correctly.

This is especially true when you find yourself reinstalling or removing a carburetor for cleaning or repair. Pay attention to your bowl fix carburetor problems, and look closely when installing components back by a fuel tap.

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My father, and his father before him, and his father; for the past 3 generations, my family have always been into gardening. The green fingers is a gift passed down to me and I thoroughly enjoy it! I also have worked in the manufacturing department for Bosch and DeWalt so I like to think I know a thing or two about tools and such!
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