Air Filter Maintenance

We’ve had several people request information on air filter maintenance. Performing routine maintenance on the air filter is really pretty simple:

  1. Remove the filter.
  2. Separate the inner and outer elements, assuming you have two elements.
  3. Immerse each element in a pan of cleaning solvent and wash it.
  4. Squeeze the element to remove the excess solvent. Be careful not to wring or twist the element or it could rip or crack.
  5. Gently wash element with warm soapy water, removing all of the dirt.
  6. Rinse with clean water and squeeze the element to remove all excess water.
  7. Inspect for tears or cracks in the foam or seams. Replace the elements if damaged.
  8. Hang elements to dry.
  9. Re-oil each element. This is the trickiest part. I usually do it one of two ways. The first is to put the element into a clear plastic bag and pour some oil in. Slowly work the oil into the element making sure to cover the entire element. Finally, carefully squeeze out any excess oil. The other option is to skip the plastic bag and put on a pair of disposable gloves. Pour some oil on the element and work it in. Repeat until the entire element is covered. As above, carefully squeeze out any excess oil.
  10. Reinstall the filter elements. Apply a thin coat of grease to the sealing surface of the assembly before installing.

Pretty simple eh? If you’re like most folks a couple of questions come to mind. What kind of solvent should be used? What kind of oil should be used? For the solvent, I’ve used just about everything — gasoline, kerosene, special filter cleaners, etc. For the oil, again, I’ve used just about everything including motor oil and “filter” oil. I’ve even heard that chainsaw bar oil is good (it’s tacky and cheap — gee sounds familiar) but I’ve never tried it. Currently I use UNI Foam Filter Oil. This stuff is about as sticky and gooey as it gets. Anyway, I decided to ask the pros what they thought. How did I decide whom to turn to? Well, UNI filters were used this year by all factory Yamahas — Henry, Dowd, etc.; as well as Team Suzuki — off road Champ Rodney Smith, Hatch and Edmondson; Team Kawasaki, including Jeffro; and a few others like ATV champ Tim Farr, 4-stroke champ Lance Smail, and desert pro Ty Davis! But more importantly I have used them for years. In fact one of the first things I do to a new bike is replace the stock filter with a UNI filter, usually before my first ride. So with this in mind, we contacted the folks at UNI Filter, Inc., specifically Tony Shumaker, V.P. Marketing, and asked him a few questions.

AOR: “Most people, such as myself, have used gasoline at one time or another to clean their foam filter. Other than the obvious dangers involved, are there any other problems with using gasoline, such as deteriorating the foam in the filter?”

Tony: “Gasoline generally won’t hurt a quality filter element, but as you suggested the liability is such that we no longer suggest its use.”

AOR: “What do you recommend, something like kerosene?”

Tony: “Kerosene is ok. We recommend any “grease cutting” detergent or any cleaner that won’t hurt your hands. Of course we recommend our own UNI filter cleaner because it is biodegradable so it won’t hurt you or the environment.”

AOR: “Many riders have been using motor oils such as standard 10W-40 to oil their filters for years. Are there really any problems in doing so?”

Tony: “Motor oil works well, but it won’t work very long. If you are prepping the filter on Thursday and racing on Saturday it will be fine. If you prep in May and park the bike until July you will have trouble. Motor oil “drains off” of the element leaving spots of the foam “dry” where dirt will go through. “Foam filter oil” will stay on the element for months (years?) and the element will still be moist to the touch. Remember, the oil stops the dirt, the filter just holds the oil! WD40 is too thin, don’t use it on a foam filter. The desired process is for the dirt to stick to the oily foam strand. Then the piece of dirt soaks up some oil and the 15th piece of dirt will stick to the first piece of dirt, then the 35th piece sticks to the 15th and so on. With a light oil there isn’t enough moisture for that to happen, so the dirt will eventually go through. Bummer.”

AOR: “Wow, I didn’t realize that about using motor oil. Some individuals claim that oiling the filter when it’s slightly damp makes it easier to distribute the oil throughout the filter element. What, if any, problems are there in doing this?”

Tony: “Never oil a wet filter!!! The oil traps the moisture between the foam and the oil and the moisture will rot the filter. The foam will start to flake within a few months. Always be sure that the filter has been rinsed thoroughly to remove the cleaner, then let it dry completely before oiling. There are many good oils that go on thin and thicken-up after the carrier has evaporated… Speaking of oiling…. too much is not better. Saturate the filter to be sure that every strand is covered, then squeeze out all of the excess, you cannot squeeze out too much. (Pouring an “X” of oil on a wadded-up filter and trying to massage it in will almost always miss spots that will pass dirt later.) The element needs to be only moist to the touch. Too much oil causes drops of oil to be drawn into the engine causing it to run poorly (oil won’t combust!) so it acts like it is restricted. This is not good!”

We’d like to extend many thanks to Tony for taking the time to answer our questions. We hope this answered most of your questions. If not, feel free to contact us or better yet the good guys at UNI Filter, Inc


Author: Ev'mon

Experience: Riding since '81. Hardware: '94 RMX250; '97 XR600; '95 NightHawk 750; '01 WR426 Ranking: Adventurist Favorite Riding: Tight Woods & Desert Favorite Places: Hungry Valley, CA; Baja Mexico

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