How to Replace Foam Air Filter in Small Engine: Small Engine Guide

A foam air filter in a small engine is a filter made out of a sponge-like material called polyurethane foam. Its job is to catch big and small bits of dirt, dust, and other tiny particles, stopping them from getting into the engine's burning area. This kind of filter has lots of tiny holes, which helps a lot of air pass through while still keeping dirt out.

These filters are often used in engines that work in places with a lot of dust, like off-road vehicles, lawn mowers, and machines used in construction. The foam can be made with different levels of thickness depending on what's needed. Thicker foam is better at catching dirt but can make it harder for air to pass through.

Foam air filters are a popular choice for small engines, particularly in equipment that operates in dusty or dirty environments. These filters are made from a sponge-like material called foam, designed to trap both large and small particles of dirt, dust, and debris, thus preventing them from entering the engine's combustion chamber. Their open-cell structure allows high airflow while effectively capturing contaminants, making them ideal for engines that face heavy exposure to dust and debris.

Commonly, foam air filters are found in a variety of small engines including lawn mowers, generators, and chainsaws. Briggs & Stratton, a renowned manufacturer of small engines, utilizes both foam and paper filters in their engines. Older Briggs & Stratton engines often feature foam filters, and they are also present in some newer models​​. These filters are particularly advantageous in off-road vehicles, lawn mowers, and construction equipment due to their ability to handle heavy dust and dirt exposure.

Foam air filters are typically washable and reusable, which makes them a cost-effective option. They can be cleaned using warm soapy water and then thoroughly rinsed. After cleaning, the filter should be dried completely before being reinstalled. Some foam filters may require re-oiling after cleaning, depending on the manufacturer's recommendations​​.

Replacing paper foam filters in small engines is a crucial maintenance task for ensuring optimal engine performance. These filters are commonly found in various small engines, such as those used in lawn mowers, generators, and other equipment. The process involves a few straightforward steps, which can vary slightly depending on the specific engine model. Below is a general guide on how to replace these filters:

Step 1: Access the Air Filter: 

Begin by locating the air filter cover on your engine. Typically, this is found on the side of the engine. Loosen the cover screw and tilt or remove the cover to access the filter.

Step 2: Remove the Old Filter

Carefully take out the old paper air filter along with the foam pre-filter, if present. It’s important to handle them gently to avoid dislodging any debris into the engine.

Step 3: Clean the Housing

Before installing the new filter, it's crucial to clean the filter housing to prevent any accumulated dirt from entering the engine.

Step 4: Prepare New Foam Filter 

Saturate the new foam filter with fresh engine oil, then wrap it in a clean cloth and squeeze to remove excess oil.

Step 5: Assemble Filter 

Place the foam filter so that its lip extends over the edge of the air filter body.

Step 6: Reinstall Assembly 

Finally, reinstall the air filter assembly onto the carburetor

Regular replacement and maintenance of air filters are vital for the health and efficiency of small engines. It prevents potential damage caused by dirt and debris and ensures the engine operates at its best.

When maintaining your lawn mower, selecting the right air filter is crucial. The first step is to ensure that the new filter is compatible with your specific engine model. Using a filter that doesn't match your mower can lead to inefficiencies or even damage to the engine. Always double-check the model number and specifications of your lawn mower to find the perfect fit.

If your mower uses a foam air filter, proper oiling is essential. A dry foam filter might only catch the largest particles, leaving smaller but harmful debris to pass through. To prevent this, lightly oil the foam filter as per the manufacturer's guidelines. This helps trap finer particles and extends the engine's life. Regular servicing of the foam filter, including cleaning and re-oiling, is key for its effective operation.

Always refer to your engine's owner’s manual for specific instructions and recommendations regarding air filter replacement. This manual is a treasure trove of information tailored to your mower's needs. It will provide you with the right guidance on how often to change the filter, the type of filter required, and the proper maintenance procedures.

Last but not least, If you're new to lawn mower care, consider investing in a lawn mower care kit. These kits typically include everything you need to maintain your mower, such as replacement filters, oil, and basic servicing tools. They are especially handy for beginners, providing a one-stop solution to keep your mower in top condition.

View on Amazon

Replacing the foam air filter in a small engine is a simple yet essential maintenance task that can significantly enhance the performance and lifespan of your equipment. By following the steps outlined in this guide, you can ensure that your engine is protected from harmful debris and runs efficiently. Regular maintenance, including air filter replacement, is key to avoiding costly repairs and prolonging the life of your small engine.

1. How often should I replace the foam air filter in my small engine? 

The frequency of replacement depends on usage and environment. Generally, it's recommended to check the air filter every 25 hours of use and replace it at least once a season or more often in dusty conditions.

2. Can I clean the foam air filter instead of replacing it?  

Yes, foam air filters can often be cleaned with mild detergent and water. However, if the filter is torn or extremely dirty, it's best to replace it.

3. What are the signs of a dirty or clogged air filter? 

Common signs include difficulty starting the engine, poor engine performance, higher fuel consumption, and black smoke from the exhaust.

4. Do I need any special tools to replace the foam air filter? 

Usually, no special tools are required. Most air filter housings can be opened with basic tools like a screwdriver or wrench.

5. Is it necessary to wear gloves while replacing the air filter?  

While not mandatory, wearing gloves can protect your hands from dirt and oil and provide a better grip.