The carburetor in your mower’s engine is essential, so it becomes a problem for you and your lawn when it isn’t functioning correctly. Integrating regular engine oversight and maintenance into your lawn care schedule will help keep your mower’s carburetor working reliably.
What Is A Carburetor?
A carburetor is a part of an internal combustion engine that adds oxygen to fuel vapors by air intake to a ratio that produces an even stream of power to whatever the motor is attached to.
Gas-powered push mowers and riding mowers use carburetors to deliver a consistent blade movement for a level cut.
What Does A Carburetor Look Like?
Since it’s at the center of the engine’s combustion process, it makes sense that a carburetor looks like a metal heart, with its multiple chambers, valves, and connections to feed air and fuel through the engine for propulsion.
A carburetor is usually a few inches long and a couple of inches wide, fitting in the palm of your hand.
How Does A Carburetor Work?
Carburetors have two internal chambers: the first is the carburetor bowl, which is the reservoir that stores fuel to be injected into the second chamber, where it’s mixed with air and combusts, powering the pistons of the engine.
A float pin in the reservoir controls the amount of fuel that enters the bowl, helping manage the amount of gasoline flowing at any time.
When there is too little gasoline in the mixture, the engine is known to be running “lean.” This uses less fuel, but it can be straining on the engine to run on light combustion: it might sputter and die quickly, or it might overheat.
When there is too little air in the chamber, the mixture is fuel “rich,” and the engine will perform powerfully but at a high use rate of gas, which can lead to buildup of solids.
Where Is The Carburetor Located?
The lawn mower carburetor is located behind the air filter (on the side or top of the engine), which is connected to the carb for air intake. The air filter helps remove impurities and solid materials that might get pulled in, to keep the inside of the carburetor clean of buildup.
Those materials will build up in the filter, though, so those should be changed regularly.
The carburetor is connected to the fuel tank by a tube, which provides the reservoir chamber with gasoline. If you’re unsure of the carb location on your mower’s engine, you can follow the fuel line to it.
If you’re uncertain after examining it, or you want to check before, consult your model’s manual.
How Does The Carb Work With The Other Engine Components?
Fuel intake is regulated by the fuel valve, which adjusts flow and will keep the reservoir from flooding with gasoline when not in use. Fuel movement is desirable when the machine is on, but too much unused fuel in the carburetor can lead to buildup and blockage.
An engine’s spark plug delivers the ignition for combustion of the mixed fuel and air from the carburetor. Spark plugs can be a good indicator of the carburetor’s performance, and by extension, the engine as a whole.
Over time, they’ll be in different conditions based on the fuel use and mixture ratio:
- Blackened plugs show that there is a lot of buildup and fuel use and that the carburetor is running on a rich fuel mixture
- A cleaner looking spark plug that is white or colorless means the carburetor is running on too little gasoline and too much air
- A good indicator of a balanced fuel ratio is a tan or light brown spark plug
The efficacy of the carb in mixing fuel has important effects on the performance and lifetime of your engine. Spark plugs are only changed once every year or two, so even though they may not need to be changed every time you give your engine a routine inspection, they can be an indicator of overall engine health, as well as that of the carburetor.
How Do I Know If My Lawn Mower Carburetor Is Bad Or Needs To Be Cleaned?
If there is a problem with the carb, a few telltale signs will encourage you to check the engine:
- Poor performance – if there is an issue with the consistent movement of the engine, or if it halts or dies over and over, it could be a problem with the fuel ratio. This might be due to the carburetor’s connection, whether it’s dirty or not, or structural wear.
- Difficulty starting – when you start up an engine for the first time for that use, it’s called a “cold start” because the engine is cold from rest. Once it warms up, the fuel will be more easily evaporated for mixture with air and combustion. A dirty carb, or one whose internal structure is malfunctioning, might take longer to get going.
- Overheating – If the fuel to air ratio is off, it can lead to your engine overheating. When there’s too little fuel in the combustion mixture, the excess air in the chamber will heat up, warming the whole engine over time. Lean fuel mixture is the main cause of overheating.
- Black smoke – if there is buildup in the carburetor or the air or fuel filters, it might burn as the engine heats up, resulting in worrying black smoke. Usually, this can be remedied by cleaning the carb.
When you inspect the carburetor for structural damage, you may find some of the components have been worn down or degraded and are interfering with the process. A carburetor repair kit will come with replacement washers, screws, gaskets, springs, and pins that you can remove and install yourself.
Peripheral components, like the air and fuel filters, or the fuel line, might also be degraded or full of buildup and may need to be replaced. Often, however, the signs mentioned above are the symptoms of a dirty carburetor.
Cleaning A Carburetor
If you’ve decided that the carb needs to be cleaned rather than replaced, you can clean the lawn mower carburetor without removing it. After disconnecting the battery line from the engine to be sure it won’t start, you can remove the air filter with a screwdriver to expose the carburetor.
You can put carb cleaner in your lawn mower by using an aerosol spray cleaner. There are specific carburetor cleaner formulas available, and WD-40 can often do the job. Usually, the need is to loosen solid buildup inside the carburetor’s bowl or the jet that transfers it from the reservoir to the mixing chamber.
The diameter of this inter-chamber jet plays a part in how much fuel is transferred between chambers, as well as how easily it may get clogged.
If you notice any rust or buildup on the outside of the carburetor, you can use sandpaper to wipe it off. This will prevent rust and corrosion from spreading.
How Much Does It Cost To Fix A Lawn Mower Carburetor?
Maintaining your lawn mower’s engine in good condition will take regular monitoring and a small investment in materials, but a few small steps will extend the life of the machine and save you from having to replace the whole thing following an engine burnout.
A repair kit costs between $15 and $40, and a replacement carburetor will run from $60 up to one or two hundred dollars.
If regular maintenance or DIY repair won’t solve your engine problem, having a professional examine the engine for troubles might cost you a little more, but it can also be more cost effective than total replacement of your lawnmower.