A Dirt Bike has to Breathe...
and
A Dirty Air Filter isn't gonna cut it

Seeing that dirt bike air filters are coated in a tacky substance to prevent dirt and other fine particles from passing through the element, they seem to have a way of getting unrecognizably dirty in what seems like no time, but considering the conditions they are put through, it really should be no surprise, and when the time comes to give your filter a freshening up this article will show you how to do it in the best way possible.

Considering the consequences of neglecting a dirt bike's air filter are:

A noticeable lack of power (which you have been spending so much money on increasing with aftermarket parts)
or
Carburetion or fuel injection problems and motor damage, It should go without mention that routine air filter maintenance is something that should be done regularly for those reasons alone.

This page on air filter service is divided into 3 main sections to make finding the info you need as easy as possible, and you can go to the section that applies to you directly by clicking the appropriate link below.

Cleaning, Oiling and Reinstalling a Foam Filter
Servicing a Pleated Type Filter
2 Things you can do to Extend the Time Between Filter Cleanings

Cleaning, Oiling and Reinstalling a Foam Filter

Before getting into too much info, It's important to make sure you know that during removal of the air filter from the air box, it is important to do so carefully so as to prevent any dirt from falling off of the filter and finding it's way into the intake tract.

And Before you go any Further...

Once you have the filter off it's a great idea to inspect the filter element before cleaning for signs of dirt passing through, tears in the filter, or seams of the filter coming apart, as well as taking a look inside the air tract with a flashlight for any signs or evidence of dirt leaking in through the air box to intake boot seal. An air leak between the air box and intake boot can lead to carburetor or fuel injection troubles and motor issues you don't want to know were even possible, and would probably rather avoid.

If it seems that any dirt or unfiltered air is being introduced to the airflow at the area of the air box to intake boot seal, be sure to see the article on sealing your air box before you ride again.

Note: Immediately after removal of the air filter, cleaning of the sealing flange and inspection or cleaning of the intake tract, it is highly recommended to install a clean rag inside the intake boot (at aminimum) and / or cover the opening with an air box cover to prevent anything (Dirt etc.) from making it's way into the intake tract while the filter is removed.

Generally, the best way to clean and service an air filter is with bio-degradable filter cleaning and oiling products which will be documented in the steps below yet most of the processes below after the steps specific to No-Toil are the same regardless of which type of cleaner or oil is used.

A familiar bio-degradable, non-toxic product used by many dirt bike enthusiasts is "No-Toil" and it is an excellent option, or alternatively a bio-degradable product manufactured by "Twin-Air" is an excellent choice as well.

The Air Filter Cleaning Process

If you have previously oiled an air filter, or have an air filter that is pre-oiled with some of the more common petroleum based filter oils and wish to use a bio-degradable product in the future, it will be necessary to first wash the filter, cage and retaining bolt or clip (If equipped) in a solvent that will break down the oil presently being used, and "Gasoline" is NOT a good idea.

Twin-Air manufactures a cleaner that will safely make short work of whatever type of oil was used previously although if this is not immediately available and you want to ride but you don't have a clean filter, use a mineral spirits type of solvent with a low flash point first, followed with a good cleaning using dish washing detergent, then finishing by rinsing well with clean water before continuing.

If you are starting with an air filter you oiled using No-Toil or purchased pre-oiled by No-Toil you can use the steps below and come out of this operation each time with clean hands and not reeking like gas or other harsh chemicals which always sucks, not to mention avoiding the chance of ever causing severe burns to yourself and everything around you in the event of a fire.

If you're using No-Toil...

Begin with adding about 2 gallons of fresh clean water to a bucket then add a handful or about a cup of No-Toil cleaning powder to the water.
Next, with the No-Toil cleaning powder in the water use your hand to stir the water around and dissolve the cleaning powder.
Once the cleaning powder has dissolved place the air filter in the solution and allow it to soak for a few minutes which will cause the oil to begin breaking down making cleaning easier.
With the filter in the solution, use your hands to work the filter around agitating it and massaging it until it appears clean.
Remove the filter from the solution once it appears fairly clean and rinse it well using a water hose with light pressure such as from a common garden hose style water gun from the inside out first, then use the water in sort of a cross flow method and invert the filter continuing to rinse until all the remaining dirt is absent.
Lastly, Before dumping out the cleaning solution it's a good idea to toss the air filter cage and securing bolt or clip (If equipped) into the solution, allowing the cleaner to dissolve any filter oil on these parts, again following by rinsing with clean water.

Regardless of which cleaning method used, once the filter is clean, allow it to fully dry before continuing.

After you're done cleaning the filter, you can remove some of the excess water from the filter by squeezing it but do NOT wring it as this can cause the seams to come apart creating a spot for unfiltered air to pass through.

If you're pressed for time, blotting the filter with paper towels followed by a short trip into the clothes dryer will usually accelerate the drying process.

Once the filter is clean and dry inspect it again thoroughly before oiling to ensure no dirt is remaining, or any of the seams are coming apart as a result of the cleaning methods or supplies used. Foam filters have seams that are commonly glued together and repeated cleanings or use of some cleaners will occasionally break this bond causing a leak in the filter allowing unfiltered air to be drawn in which is never good as this greatly accelerates the wear of every internal engine part, as well as causing carburetor or fuel injection problems.

Applying the Oil and Reinstalling the Air Filter

It is critical to use an oil that is designed specifically for use on foam air filters in the following steps to prevent dirt and other fine particles from passing through the pores of the filter.

Using the filter oil of your choice (No-Toil is the recommended filter oil around here) apply the filter oil liberally to the outside of the air filter element, as well as the area where the filter seals to the air box, working the oil into the foam by hand achieving a uniform coverage.
Once the filter is uniformly covered with filter oil install the filter cage inside the element along with the bolt to secure the filter while ensuring the cage is installed properly inside the filter element.

Moving right along...
Considering that filter oil is a very tacky substance lay the filter open side up on wax paper or a paper towel before continuing so as to not make a mess on the bench or have anything stick to the filter.

Using a filter rim grease, (Currently at the time of writing only No-Toil manufactures a bio-degradable product for this and Twin-Air feels greasing the sealing ring area is unnecessary).

Although use of a rim grease manufactured by No-Toil is recommended, the choice is yours whether to use this or not.

If use of the sealing grease is desired, apply it to the sealing area of the filter in a nice and uniform coverage mainly focusing on the center of this area, as it is not necessary to apply the sealing grease to the entire width which causes a mess for future cleanings, and is a waste of product.

Once the air filter is prepared for re-installation, remove the air box cover from the opening and / or the rag from inside the intake tract checking to be certain the sealing flange is clean and free of any grease or oil that may be remaining from the previous filter, then checking again for any dirt or other particles to have fallen into the intake tract before reinstalling the filter.

After you've cleaned the sealing flange and the intake tract is cleared of any foreign particles, reinstall the filter ensuring the locators on the filter cage are properly indexed, then reinstall the seat, side panel or whatever you had to remove to access the air filter and get your riding gear on.

"It's time to Air this thing out..."

Servicing a Pleated Type Filter

When beginning the cleaning and service of a pleated type filter, it is advisable to follow the same recommendations as described above concerning removal of the filter, inspection of the filter element before cleaning and inspection of the air box and intake tract for any dirt or other particles as well as covering of the intake tract while the filter is removed.

Servicing of a pleated type filter is not difficult but requires an entirely different technique than that of a foam type. Below are some recommendations that should get you started in the right direction, although due to the differences in cleaning and servicing methods from one manufacturer to another of these type of filters, it is advisable to only follow what your specific filter manufacturer recommends. With that...

Cleaning a pleated type air filter is usually best done with light pressure from a compressed air source forcing dirt and particles away from the air filter pleats, working from the inside outward or using a vacuum cleaner to draw contaminants (dirt) away from the filter before further cleaning.

There are available cleaners for use on pleated type filters designed to safely dissolve the oil applied without harming the filter's materials, but check with the manufacturer of your specific filter before using any chemicals, cleaners or water on the filter so as to not damage the filtering material, rendering the filter useless and unable to prevent contaminants from being drawn into the air stream.

Once you have obtained the proper cleaner for your brand of air filter it's a good idea to follow the manufacturers directions for how to best clean and service the filter so as to not cause damage to the air filter possibly compromising its sealing and filtering abilities as this could potentially allow dirt and unfiltered air to be drawn in greatly accelerating the wear of every internal engine part and causing carburetor or fuel injection problems, none of which are any fun.

After you have cleaned the filter and it has been allowed to dry completely it will need to be oiled so as to trap dirt and fine particles, making them unable to pass through the element.

There are oils designed specifically for use on pleated type filters, but check with the manufacturer of your filter for the type of oil they recommend otherwise you may risk damaging the filter with the chemicals in the oil, or be unable to clean the filter at a later time due to the cleaner that is recommended and the oil that was used being incompatible resulting in the ruining of the filter when a future cleaning is attempted.

2 Things you can do to Extend the Time Between Filter Cleanings

Remember;
"I Ride also" therefore I know how much of a hassle it can be having to clean an air filter so you might find this section of air filter maintenance to be enlightening. After all, Who wouldn't want to stretch filter cleanings out further?

Ideas I've found over the years to extend the time between filter cleanings that work well are:

Purchasing more than 1 filter (A total of 3 is ideal) and swap out filters with a new, clean filter, pre-oiled (By You), washing and servicing all 3 together when you have dirtied them all, keeping the pre-oiled "Spares" in Zip-Lock gallon size freezer bags until you are ready to use them. Although, If you are using this technique be sure to clean the sealing flange on the air box, and always inspect the air tract for any dirt or other particles before installation of a new filter.

If you really want to avoid the filter cleaning chores and stretch air filter cleanings out even further, it's painless to purchase some filter skins, or filter covers and keep these over the filters your installing on the dirt bike, but don't only swap out filter skins or covers with the idea of never servicing the filter attached to the dirt bike. The oil you are using on the filter may dry out over time making it less effective at trapping dirt, as well as swapping out filter skins or covers likely disturbs the filter that is installed and could potentially allow dirt or other particles to find their way through the primary filter into the intake tract resulting in dirt or other abrasive particles to be drawn in potentially causing carburetor or fuel injection problems and accelerating the wear of every internal engine part.