How to Change the Air Filter in a Lawnmower (Briggs & Stratton Engines)

July 30, 2008 | by Fred (email) |

Performing full lawnmower maintenance at least once a year is essential to keep your mower in top running condition.  This article is the second in a series of lawnmower maintenance articles that together cover complete lawnmower care.  While this article focuses on changing the air filter in a push lawnmower, the basic principles can be applied to a riding mower and all other 4-cycle gas powered yard equipment (including such things as a pressure washer or chipper shredder, for instance).

We’re performing maintenance on both a Craftsman 6.5 horsepower (HP) self-propelled mower, and a lighter duty 4.5 HP Murray mower.  Both push mowers are powered by Briggs & Stratton 4-cycle engines.

Changing the air filter in a lawn mower is easy for even the most novice DIYer and is the most basic thing you can do to improve your mower’s fuel efficiency.  Aside from the time required for a trip to the store to buy the replacement part, the entire operation can be completed in under 10 minutes.  One note before we begin:  These instructions are for general knowledge only and are not endorsed by the manufacturer.  You should always follow the maintenance instructions that were included with your lawnmower.

How to Change a Lawnmower Air Filter

Step 1: Locate the air filter.  On our Craftsman mower, the filter is located under a black plastic cover on the side of the engine, secured by a single flat-head screw to the crankcase [see picture to the right].  On the Murray, the filter is encased in a black plastic dish and cover setup, with a single screw that runs down into the crank case [not shown].

Step 2: Unscrew the filter cover and determine whether the air filter needs to be replaced.  Our Craftsman lawnmower uses a standard paper type filter (shown on the left in the picture below)  You can see from the picture that it is in dire need of replacement.  On the Murray, the filter is a sponge material (shown on the right in the picture below).  The sponge is caked with oil and should be cleaned or replaced.

Step 3: Purchase a matching filter or clean the filter for re-use.

Standard paper filters should always be replaced with a new one.  You can find the right filter for your lawnmower at most home improvement and hardware stores.  Remember that even if your lawnmower is a store brand, the engine is likely a known brand (e.g., Briggs and Stratton).  If you can’t find the right parts searching by lawnmower model number, try using the engine brand and model #.

If a sponge filter is dirty but in otherwise good shape, it can be cleaned using a mild grease cutting detergent.  Soak the sponge in warm soapy water and rub until clean.  Some authors have suggested running the sponge filter through the dishwasher.  In our opinion, this is overkill; and it runs the risk of getting lawnmower oil on your dishes and flatware!  The picture to the right shows our Murray sponge air filter and its compartment case cleaned up using dawn dish detergent.  Rinse thoroughly, and allow the sponge to dry completely before reinstalling.

Step 4: Clean the area around the air filter chamber and ensure no debris enters the engine.  It is not necessary to get the area totally clean, simply wiping with a dry cloth is sufficient.  Ensure debris does not enter the engine as this could damage internal parts.

Step 5: Reseat the air filter in its original compartment, ensuring it is seated corrected (paper air filters are designed to for optimal air flow in only one direction).

Step 6: Start the engine.  The engine should be running at least as smooth as it was before the filter change.  If something doesn’t sound right, check the filter to ensure it is seated properly.

That concludes the second article in our lawnmower maintenance series.  Cheers to a healthy lawn… and lawn mower!

What do you think? Is your lawnmower’s air filter overdue for a change?

11 Responses
  1. dick g says:

    how do I adjust the idle speed on the Craftman6.5 lawnmower…the spark plug ioften runs a bit faster than normal. carbon is often built up on plug..have just put a new one in ..I know its on carburator… thanks..

  2. chris says:

    I just finished my seasonal maintenance and the idle speed on my Craftsman 6.5 (917.375500) is super slow. I’m thinking the exact opposite of dick g above. HOw do you adjust this speed?

  3. Beverly Seirsdale says:

    I own a craftsman riding lawn tractor Model 28922. I have researched how to change the air filter. All information I got did not look like the air filter on my mower. Can you help?

  4. Perla says:

    thanks for showing where the air filter is located! (can’t find manual :\ ) … checked… it needs new one very bad!

  5. Doug says:

    @ Dick G and Chris –

    These engines are designed to not allow you to adjust the throttle. That’s why, unlike the old school lawnmowers, there’s no throttle speed adjustment. I think it has to do something with meeting emissions regulations.

    That being said, there is a way to adjust it, which I found out because I thought my engine was running too slow. Your setup may vary, but on my lawnmower, there is a small plastic cover above the housing for the air filter that can be removed with a screwdriver – single screw holding it on. Under that cover, there is spring under tension between a fixed metal plate and the mechanism that controls the throttle. With the engine running, you can GENTLY bend in either direction that fixed plate with a pair of pliers to control the amount of tension on that spring, and you should hear the engine speed up or slow down.

    Obviously they don’t want you monkeying with this, and you definitely should be careful with adjustments you make as you could probably shorten the life of your engine. You certainly will use more (or less) gas. Be careful and good luck!

  6. Laura says:

    Thank you, thank you, thank you! As the owner of a second-hand mower with no maintenance experience, I didn’t know where to find the filter. I went to the lawn mower’s manual on-line and it didn’t show the location either. ??? People aren’t borning knowing these things and when you are a widow trying to mow, they are important.

  7. dennings_jeff says:

    I want to thank you for saving me money. I know this is going to sound crazy, but I didn’t realize that you could clean the foam filter. Thanks again. JD

  8. Scott says:

    Briggs 190cc 700 series motor on my mower. Keeps stalling out as I run. Sometimes I can keep it going, sometimes it dies all together. Thoughts on what it could be or solutions?

  9. Patti Crews-McMorran says:

    This is frustrating – I have unscrewed the filter cover but it won’t disengage from the side of the engine as though something else is attached and holding it back?

  10. Katie says:

    What do I do if my lawn mower is leaking oil for the filter? Do I have to change the filter or did I put to much oil in it.

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