Selecting and Maintaining Air Filters on Commercial Lawnmowers

One of the best things you can do to maintain and preserve the life of a lawn mower or outdoor equipment engines is to service the air filter regularly. Here we discuss what an air filter does, the different types of filters, plus maintaining and cleaning small engine air filters.

What’s the purpose of a small engine air filter?

Engines need air to burn fuel. Along with the air that gets pulled into an engine comes dust, dirt, and debris. The air filter keeps debris from reaching the combustion chamber and clogging the engine. Running with a compromised air filter leads to accelerated engine wear and eventual failure. Clean removeable and replaceable air filters keep debris out of your engine and extend equipment life.

What are the signs and symptoms of a dirty or faulty air filter?

If an air filter is filled with dirt, it will:

  1. Not allow proper air to pass through the engine resulting in reduced power and performance.
  2. Eventually collapse or tear allowing debris and dirt to pass directly into the engine.

Signs that an air filter needs to be cleaned or replaced:

  1. The air filter is covered in dirt or oil.
  2. The lawnmower does not maintain consistent power. Decreased airflow = less power.
  3. The engine is burning more fuel. It compensates for the loss of power by burning more fuel.
  4. The lawnmower has starting trouble. This could be problems with air, fuel, or spark.

If the air filter is not providing the correct air flow the engine will stall, surge, and sputter as it gasps for air. Cracks or holes in the air filter will free flow debris leading to eventual engine failure.

What types of air filters are found on a lawnmower?

There are three main types of air filters on small engines:

  1. Pleated paper filters
  2. Foam filters
  3. Dual element filters – when a foam filter is used as a pre-cleaner for a paper element.

Dual element filters are more expensive but have longer life. The foam pre-cleaner increases the life of the more expensive paper element.

How and when to clean and maintain lawnmower air filters?

The best time to clean or replace an air filter is before it creates problems. Pleated paper air filters and foam pre-cleaners on the dual element types should be replaced at the beginning of the season as part of regular maintenance. Briggs & Stratton recommends a dual element pre-cleaner filter be replaced after 25 hours and the paper cartridge be replaced after 100 hours. Without a pre-cleaner the filter should be replaced every 25 hours or more depending on conditions.

You can extend the life of an air filter by regular cleaning. In general, you should check and clean a lawn mower air filter every few uses to prevent build-up of dirt and debris.

How to clean an air filter.

Air filters in operation for a long time cannot be cleaned fully. Replace the air filter at regular intervals. Damaged air filters must always be replaced. Husqvarna recommends the following:

For pleated paper filters:

  1. Remove cover and inspect air filter. If it’s dirty clean or replace it. If it’s oily replace it.
  2. For a pleated paper filter that’s not oily, tap on a hard surface to remove most of the dust and reuse. If light tapping does not remove most of the dust replace the filter.
  3. It is not recommended to blow out the air filter with an air hose for risk of tearing the paper, however, if you do, blow from the inside out to avoid further embedding particle and debris.
  4. After one or two cleanings you should always replace the filter as particles will be permanently embedded in the filter paper.
  5. Wipe down the inside of the housing before reinstalling the air filter.

For foam filters

  1. Remove cover and foam air filter.
  2. Clean with soap and water, rinse soap out, squeeze water out, and let dry.
  3. Lubricate the foam filter with oil. SAE30 engine oil is fine but filter oil is preferred. Spray the filter or put a few teaspoons in a baggie with the filter and squish it around.
  4. Remove filter and press with clean cloth to remove any excess oil. Do not overdo the oil. If it runs off in the filter housing, you have used too much.
  5. Reinstall filter and make sure it is fully and properly sealed in its’ holder.


For Dual Element Filters

  1. Follow the same procedures for the foam and pleated paper filters above.


How to find the lawnmower engine filter I need?

Air filters come in many shapes and sizes depending on engine size, brand, and model. They can be simple foam inserts to flat waffle paper to double cylindrical filters on larger equipment. It is important that you use the correct size and type for your engine.

The easiest way is to check your owner's manual for the air filter part number or look it up online. You can cross-reference any equipment manufacturer’s part number for the correct air filter at It is not necessary to buy the exact same filter from a dealer. High quality replacement filters are available on sites like Just make sure you get an excellent quality filter the fits your equipment properly. Your engine will reward you with longer life and lower maintenance costs.


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