Gas mowers come fitted with an air filter. Some are made of paper, while others are made of foam. Whichever type your mower has, its purpose is the same: to allow air through while stopping dust and dirt from passing into the engine. If you’re curious whether you can run a lawn mower without an air filter, you’re asking the wrong question. You should be asking “should I run a lawn mower without an air filter?”
And the answer is quite simple. You can run a lawn mower without an air filter. For a short while it’ll run just fine, maybe even better than before if you had a dirty filter fitted. But you shouldn’t be running a lawn mower without the air filter for long periods. It’ll damage your mower’s engine.
Why Running a Lawn Mower Without an Air Filter is Never a Good Idea
The air filter is an absolutely necessary part of the design of a small engine. It’s not an optional extra. You see your engine needs 3 things to function properly: gas, air, and a spark (I guess it’s actually 4, as it needs oil too, but the 3 I mentioned all relate to the combustion process). And it needs these things in the right quantities too. If any of these 3 things are missing or present in the wrong quantities, your mower won’t run smoothly and it might not run at all.
When it comes to the air filter, it’s obviously involved in the supply of air to the engine. It also acts like security at a nightclub, stopping the undesirables from getting in (in this case, dirt, and dust).
Now don’t get me wrong, an air filter that doesn’t let enough air through (this happens if it’s not maintained and becomes clogged) isn’t any better. As I mentioned before, air needs to be supplied to the engine in the right quantity for the engine to run smoothly.
But the consequences of running a lawn mower without an air filter for extended periods can be very severe. Without the filter, dirt and dust will make their way into the carburetor and then into the engine itself. If enough dirt gets in there, it’ll destroy the engine cylinder. Then you’re looking at either an engine replacement or an engine reconstruction, and for a lot of cheaper mowers, it’s often cheaper to chuck the whole thing and buy a completely new mower.
There’s another factor that increases the risk of this happening…A lawn mower is rolling along the ground, and it’s typically very dusty down there. A dusty environment + no air filter is a bad combination!
My Lawn Mower Won’t Start with the Air Filter in Place
Sometimes people remove the air filter because they’re having trouble starting their mower. Now there are quite a few reasons why your mower might not be firing, but it’s true that the air filter could very well be to blame.
Remember that I said earlier that an air filter must let enough air through for a gas mower to work. Well in this situation, it’s highly likely that your filter is clogged. A lawn mower air filter soaked in oil, for example, is definitely not going to let air through in sufficient quantities, so the combustion process won’t be able to take place. There’s gas, a spark, but the air is missing.
You’ll find that if you remove it, your mower will start up, because air is now being supplied to the engine. But running a lawn mower without an air filter is a temporary solution. In fact, I wouldn’t call it a solution at all. It’s more of a quick way to test whether it’s definitely the air filter that is causing the problem.
Lawn Mowers and Air Filters: The Bottom Line
Don’t run a mower without an air filter in place for any longer than a few minutes if you don’t want to be shopping for a new mower in the near future.
It’s vital that you not only have an air filter properly installed at all times when using your mower, but that you regularly maintain it too. Dirt and debris will build up on the outer edge of the filter over time – that’s the whole idea – and this needs to be removed so that proper airflow is maintained.
Foam filters can usually be washed and re-installed, whereas with paper air filters you are better off just replacing them. Both types of filters are cheap to buy, which is even more reason not to run your mower without one!