Most lawn mowers are rugged machines that can run for years. But don’t make the mistake of thinking just because a mower is running, that means it’s performing well. Often, that’s not the case. Maintenance is crucial to keeping your mower running optimally, and I recommend that most homeowners complete annual maintenance twice a year – in the spring to get your mower ready for the season, and in the late fall to winterize your mower and prepare it for storage. Today, I’ll explain how to clean an air filter on a lawn mower, and why you absolutely need to do it regularly.
I’ll also explain why annual replacement of your mower’s air filter is a simple, low-cost DIY project anyone can (and everyone should) do.
This article was last updated on by Lawn Chick Owner Sarah Jameson
Article content reviewed for accuracy by Certified Horticulturist Nicole Forsyth, M.S., and by Horticulturist Arthur Davidson, A.S.
Why Your Mower’s Air Filter is Important
The air filter is one of the most important parts of your lawn mower when it comes to day-to-day performance.
If your mower starts but isn’t cutting grass properly, or seems to get bogged down easily there’s a good chance the air filter is causing the problem.
All combustion engines need air to function, so sucking in air is an essential part of the process.
Problems happen if dirt and debris gets pulled into the engine along with the air. When this happens it can lead to failures and your lawnmower not starting.
Air filters prevent this issue by allowing air to pass through to your engine while blocking all the debris, such as grass clippings, twigs, sticks, leaves, dust, and dirt.
Still, all air filters become dirty or blocked over time (that just means they’re doin their job). When they get dirty and clogged less air gets to the engine, causing problems. That’s why keeping your mower’s air filter clean is an important part of mower maintenance.
The good news? Cleaning or replacing an air filter is one of the easiest mower maintenance tasks.
Depending on your type of mower, the air filter could be located on the side or top of the engine, and it will be pretty easy to recognize.
In all models, the filter is easy to access, though it may be behind a plastic cover.
Usually it has a single screw-on or snap hinge cover holding it in place.
Below, I’ll explain what you need to know about how to clean and replace your mower’s air filter.
I’ll talk about air filter types, how to find out which kind your mower has, where to find the filter, and how to clean it.
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Types of Lawn Mower Air Filters
There are several different types and styles of air filters used in lawn mowers, and it’s important that you identify what kind of air filter your mower uses so you can clean and service it properly.
Usually mowers have either a:
- Paper Filter,
- Foam Filter, or
- Combination Filter.
Below I’ll tell you a bit about each type of mower air filter.
Paper Air Filter
A paper filter looks like a paper accordion. It works by having perforated paper with tiny holes in a folded construction.
Air can pass through the microscopic holes, but debris cannot.
While you may be able to clean your paper filter, you’ll definitely need to change it for every 25 to 50 hours of mowing use.
On my self-propelled Honda mower, the paper air filter is located on the side of the mower’s engine under a rectangular plastic cap that is pressure-mounted and easy to remove.
The filter inside is just held in place with the housing, so I take out the filter, shake it gently and blow air across the paper fins to remove any big debris particles prior to use.
A replacement paper lawnmower filter costs about $8 and you can find one that will fit at just about any local hardware or big box store.
TIP: If your mower is difficult to start, you can remove the paper air filter and spray Gumout starting fluid into the hole behind the filter just before you mow. Once you’ve sprayed some in, replace the air filter and casing and start up your mower with the pull cord. This will help your mower start up easily and will also keep your carburetor clean and free of corrosion. One can will last you a few years.
Foam Filter
A “foam only” filter works in a similar way to paper but has a different filtration material. A foam piece coated in motor oil traps all types of dirt, dust, and debris.
The motor oil is an important part of the system because it stops the smallest of dirt particles. Without motor oil, the foam filter will only capture the largest debris, and you’ll end up with a dirty carburetor that needs to be removed and cleaned.
If your mower has a foam air filter, it is essential to re-coat the filter with motor oil every three months or 25 hours of use.
Combination Filter
Combination filters are the best air filters in the mowing world because they combine foam and paper elements to keep your engine running clean.
The foam acts as a pre-barrier for the paper element, helping to add more life to the paper (which is more expensive to replace).
Because air passes through two layers of filtration, it is significantly cleaner when it reaches the engine.
How to Replace a Lawn Mower Air Filter
Replacing a lawn mower air filter is simple and easy.
Here are the steps.
- Locate the air filter housing on your lawn mower. The location will depend on the mower type. For example, on a tractor mower you will need to lift the engine cover, while a walk-behind mower usually has the engine exposed. The air filter is typically on top, on the front, or the side of the engine, located in a plastic or metal housing.
- Open the housing by either unscrewing the lid or opening a hinge, depending on your mower.
- If your lawn mower has a foam pre-filter, remove it, and inspect it. Sometimes cleaning the foam and re-covering it in motor oil is fine. However, if the foam has become stained, brittle, or hard, it needs to be replaced.
- Moving on to the main filter. If your air filter is paper, give it a gentle tap to remove excess dirt. If the paper is blocked, then the filter must be replaced. To check, hold the filter up to a light or the sun. For foam air filters, again check for staining, hardness, or general disrepair before replacing it.
- Dispose of the old air filter.
- Insert your new air filter into the housing after cleaning the assembly.
- Reattach any protective layers and then close the housing lid. During the entire replacement process, be careful not to damage or pinch the new air filter. Any holes in the filter will allow large debris to pass into the engine.
Replacing Different Types of Lawn Mower Air Filters
As well as foam, paper, and mixed filters, it’s also worth noting that some air filters are reusable while others are disposable.
What this essentially means is that you can clean some filters for reuse, while others must be replaced and cannot be cleaned. In fact, doing so may degrade their performance and put your mower at risk.
In general, paper air filters are disposable and foam lawn mower filters are reusable.
You can gently blow on and partially clean off a paper air filter mid-season, but I don’t recommend using compressed air on them – if it looks too dirty to function well, just buy a new one for under ten bucks.
It’s a small price to pay to keep your mower working well for years to come.
Why Air Filter Maintenance is Important
Your lawn mower won’t run (for long) without an air filter.
Engines need air but cannot deal with the debris and other items that may end up lodged inside if there’s no filter.
Air filters do all the dirty work to ensure your lawn mower runs seamlessly. However, occasionally you need to clean or replace the filter.
If enough debris gets into your engine, it’ll get clogged and won’t perform as it should.
That’s why regularly replacing the air filter is a wise move if you want to your mower to perform well for years to come.
When to Change the Air Filter on Your Mower
A common question is how often the air filter on a lawn mower needs to be changed. Most experts recommend that you check your mower’s owner manual for specific guidance that applies to your specific mower.
But you’re on the internet looking for the answer you need now.
My Recommendation
How often you need to change the filter on your mower can depend on a variety of factors, such as how often you use your lawn mower and in what conditions.
Needless to say, mowing three times a week in a dusty location is going to mean you need to change the air filter more frequently.
And when you’re mulching leaves in your yard there will be more dust kicked up and your filter will be working overtime.
Most homeowners can usually get away with changing their filters once a year. This means changing the filter around every 25 to 50 hours of use.
Whether you have a foam filter or a paper one, you can replace it with a new one by yourself, and it will take you 15 minutes (and probably much less) in your garage.
Replacing my paper air filter requires no tools and about 20 seconds of my time (including throwing the old one in the trash).
My best advice is to replace your filter annually, and visually inspect it before every mow.
Clean Your Lawn Mower Air Filter Regularly, Replace Annually
Time goes by quickly, so make sure to keep track of when you last changed your mower’s air filter.
As part of my spring mower maintenance I always install a brand new air filter in my mower.
But if you haven’t changed or cleaned your mower’s air filter, it’s a low-cost and easy fix to get your mower running like new again.
Hopefully this article has given you the information you need to keep on top of it going forward!
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-Sarah
