Expert Says Take Care Of Air Filters On Small Engines

Linda Benedict  |  3/15/2006 1:47:58 AM

One of the best things you can do to maintain and preserve the life of a small engine is to service the air filter regularly.

News You Can Use For March 2006

Many homeowners have several small engines in the garage or tool shed on equipment like a lawnmower or string trimmer. Some may also have a garden tiller, a hedge trimmer, a lawn edger or a chainsaw. Most of these small engines have an air filter.

"One of the best things you can do to maintain and preserve the life of a small engine is to service the air filter regularly," says Dick Parish, an engineer at the LSU AgCenter’s Hammond Research Station.

Parish says lawn and garden equipment often operates in dusty, dirty conditions, and every engine needs to breathe in fresh air to mix with the fuel for burning. Any dust or dirt drawn into the engine with the intake air will not only clog carburetors and air passages but also cause internal engine wear.

"Dirty air can ruin an engine very rapidly," Parish says, pointing out that air filters are designed to trap the dust and dirt in the incoming air before the dirt particles can reach the engine. Since lawn and garden engines are operated in such dirty conditions, the filters can become filled with dirt fairly rapidly.

"Unless you drive a lot of unpaved roads, you probably don’t need to change the air filter in your car more often than every few years," the engineer says. On the other hand, "Your small engine air filters need servicing much more often - perhaps after 2 to 4 hours of operation."

Parish says that if the filter fills with dirt, two things can happen. First, the filter may plug and not allow enough air into the engine, reducing power and performance. Second, the plugged filter may collapse and allow dirt to pass directly into the engine.

"The way to avoid these problems is to service your air filters often, and the best place to start is with the operator’s manual," Parish says. "It will tell you how to service the filter and suggest a frequency for service, often stated in hours of operation.

"It’s a good idea to check your air filter even more often than suggested until you get enough experience with your machine to know how fast the filter loads up," he adds. "A tiller in a dry, dusty garden or a garden tractor mowing tall, dry weeds will load air filters faster than a lawnmower used on a lush, well-watered lawn."

To check the air cleaner, remove the cover and look at it. If it’s dirty, clean or replace it, Parish says. Most small engines use a pleated paper primary filter. Tap it lightly on a hard surface to knock off most of the dust and reuse it if it’s not oily.

"Do not try to blow it out with an air hose," Parish says. "There’s a risk of puncturing it."

If it’s oily or light tapping doesn’t clean it, it should be replaced, he says, adding that it should also be replaced after one or two cleanings.

Along with the primary filter, some engines also have a foam prefilter that either wraps around a round pleated-paper primary filter or fits above a rectangular primary filter. Foam prefilters can be washed with lots of hot water and soap, dried by squeezing it in paper towels or letting it air-dry and then re-oiled.

"It’s essential that foam filters be oiled prior to use," Parish says. "Just pour about one to three teaspoons of clean engine oil onto the foam before installing it and massage the filter to work the oil into it uniformly. Rubber gloves are very handy at this stage. Then, just reinstall the foam prefilter.

"Don’t overdo the oil," he warns. "If it runs off onto the filter housing, you have used too much."

Since foam prefilters are generally inexpensive, Parish suggests just replacing the foam element rather than cleaning it. But even new foam filters will need to be oiled prior to use.

Parish cautions to be very careful when removing or installing filters to avoid knocking dirt or dust into the engine. Clean the housing before removing the filter to minimize the chance of knocking dirt inside.

He also cautions to be sure to use the correct size and type filter for the engine.

"It’s not necessary to buy a same brand filter from a dealer," he says. "You can get good filters at some auto parts stores. Just be sure you get a good-quality filter that fits properly. Improper fit can allow dirt to enter the engine."

Parish says to use the manufacturer’s recommendations as a general guide but to service the filters more often if operating conditions are very dusty or dirty. And be sure to oil foam prefilters.

"Your small engine will reward you with lower repair costs and longer life if you give it clean air to breathe," he says.


Contact: Dick Parish at (985) 543-4125 or

Editor: Rick Bogren at (225) 578-5839 or

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