All-OffRoad - Tech-Tips
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:
- Remove the filter.
- Separate the inner and outer elements, assuming you have two elements.
- Immerse each element in a pan of cleaning solvent and wash it.
- Squeeze the element to remove the excess solvent. Be careful not to wring or twist the
element or it could rip or crack.
- Gently wash element with warm soapy water, removing all of the dirt.
- Rinse with clean water and squeeze the element to remove all excess water.
- Inspect for tears or cracks in the foam or seams. Replace the elements if damaged.
- Hang elements to dry.
- 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.
- 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
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
Tony: "Gasoline generally won't hurt a quality filter
element, but as you suggested the liability is such that we no longer suggest its
AOR: "What do you recommend, something like
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
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
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
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...