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How to Service A Dirt Bike's Air Filter


Frequent and proper service of a dirt bike's air filter is critical to the performance and longevity of your motor, and since dirt bike air filters are coated in a tacky substance to prevent dirt and other fine particles from passing through the element, they often get unrecognizably dirty in no time, and when the time comes to clean your air filter, it's important the filter is properly oiled and reinstalled so it's sealed to the air box as we'll show you, otherwise the motor could draw in unfiltered air resulting in costly engine damage, as commonly occurs with a damaged, or improperly installed air filter.

Remember, the potential consequences of neglecting a dirt bike's air filter include:

  • A noticeable lack of power, throttle response and performance.
    (which you've been spending money to increase with aftermarket parts)
  • Carburetion or fuel injection troubles, and / or
  • Engine damage.

How to Access and Remove A Dirt Bike's Air Filter

Always remove the filter from the air box with care to prevent dirt from falling into the intake tract.

Accessing the air filter on most dirt bike's and off-road motorcycles is usually accomplished by removing the seat or a side panel, then removal of the filter element will be possible after removing a center bolt or clip which secures the filter element to the air box, although if you need additional help locating or removing the air filter, you may want to refer to a service manual specific to the motorcycle being serviced for manufacturer specific instructions.


Hold On Before You Run Out & Pull the Filter Off...

After you've removed the air filter from the motorcycle, be sure to inspect the filter element before cleaning it while looking for dirt passing through the element, tears or separations in the filter, or evidence of the filter coming apart, while always replacing any filter that appears torn, or is otherwise compromised.

Looking Into Intake Tract of A Dirt Bike

Additionally, while the filter is removed, be sure to take a look inside the intake with a flashlight while looking for evidence of dirt being drawn into the intake from an improperly installed and sealed air filter, or from a leak where the intake boot meets the air box, both of which conditions can allow the engine to draw in unfiltered air which often leads to carburetion or fuel injection troubles, and motor problems you don't want to know were even possible.

Dirt in the Intake of A Dirt Bike Carburetor


If there was dirt visible in the intake tract, the carburetor and engine will have ingested dirt and other fine particles, and at a minimum you will need to remove, disassemble and clean the carburetor, while strongly considering an engine tear down to inspect the piston and cylinder walls and repair, or replace any parts worn by the abrasive particles being drawn into the intake tract, then during reassembly, be sure to check out our article on sealing your air box so you can ensure the motor is not drawing in unfiltered air in the future, nor allowing water into the intake through water crossings.

Image of an Air Box Cover
Immediately after removal of the air filter, cleaning of the sealing flange and inspection of the intake tract, it's highly recommended to cover the opening with an air box cover, as these will enable washing of the air box, and prevent any contaminants (Dirt) from getting into the intake tract while the filter is removed.

How to Clean and Service A Foam Motorcycle Air Filter

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

What Should I Use to Clean My Air Filter?

If you have an air filter that has been previously oiled with some of the common petroleum based filter oils, and you're wanting to use a bio-degradable product, it's best to toss the old filter and start with a new filter, although if that doesn't interest you, it'll 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 Recommended for Cleaning Any Air Filter.

Twin-Air manufactures a reusable 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.

Which Air Filter Oil is Best?

A familiar bio-degradable product used by us, as well as many other racers and dirt bike enthusiasts is No-Toil and it is an excellent option. Alternatively, a bio-degradable filter oil manufactured by Twin-Air is an excellent choice as well, as both are environmentally friendly, don't require gloves and are much less harmful to your skin and the environment during cleaning's than other harsh chemicals.

How to Clean A Foam Air Filter Using No-Toil Cleaner

Picture of Rinsing an Air Filter from the Inside Out

If you're working with an air filter that's been previously oiled using No-Toil, (or you use No-Toil going forward) 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 you'll be avoiding any chance of ever causing severe burns to yourself, and everything around you in the event of a fuel based fire.

  1. Begin with about 2 gallons of fresh water in a clean container, then add a handful of No-Toil Cleaning Powder to the water and using your hand, stir the water around to dissolve the cleaning powder.
  2. Once the cleaning powder has dissolved, place the air filter in the solution and allow it to soak for a few seconds which will allow the oil to begin breaking down, making cleaning easier.
  3. With the filter in the solution, reach in and work the filter around, agitating and massaging the filter until the filter oil has fully dissolved and the air filter appears clean.
  4. Once the filter is clean, remove the filter from the solution 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, while also inverting the filter and continuing the rinse until any remaining dirt is absent.
  5. Lastly, Before dumping out the cleaning solution, toss the air filter cage and securing bolt or clip into the solution, allowing the cleaner to dissolve any filter oil on these parts, again followed by rinsing with clean water.

Make Sure the Filter is Dry and Not Coming Apart

Image of Squeezing the Water from a Clean Filter

Regardless of the cleaning method used, squeezing the excess water from the filter greatly speeds the drying time, just DON'T wring a foam air filter, as doing so can cause the seams to separate, allowing unfiltered air to pass through.

With a clean and dry filter element, be sure to inspect the seams for evidence of coming apart as a result of the cleaning methods or supplies used, while discarding any compromised air filter, as foam filters have bonded seams and repeated cleaning's, or use of some cleaners can break this bond creating a leak in the filter, allowing unfiltered air to be drawn in which is never good, as this greatly accelerates the wear of internal engine parts, and wreaks havoc on the induction system.

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

How to Properly Oil and Reinstall A Foam Air Filter

Image of a Properly Oiled and Installed Air Filter

First of all, It's critical that you use an oil designed specifically for use on foam air filters, as filter oils are designed to be tacky, which prevents dirt, and other fine particles from passing through the pores of the filter.

  1. Using the filter oil of your choice (No-Toil is what we use) and disposable gloves, apply the filter oil liberally to the outside of the air filter element, including the flange where the filter seals to the air box, while working the oil into the foam by hand until a uniform coverage is achieved.
  2. Once the filter is uniformly covered with filter oil, install the filter cage inside the element, while ensuring the cage is installed properly inside the filter element by aligning any indexing locators, as can be seen in the following picture at about 1:00.

How to Grease the Sealing Rim (Optional)

With the filter oiled and properly located on the cage, it helps to lay the filter open side up on wax paper, or a paper towel before continuing so you don't make a mess on the bench, or have anything stick to the filter.

Image of an An Air Filter with Rim Grease Applied

If use of a sealing grease is desired, No Toil makes a bio degradable filter rim grease, so do NOT use a petroleum based grease if using a bio-degradable oil, and apply the grease to the sealing flange of the filter while creating a uniform coverage, but only cover the center of the sealing flange, as it is not necessary to apply the sealing grease to the entire width, which causes a mess at future cleaning's, and is a waste of product.

If You're Using A Petroleum Based Filter Oil,
You Can Grease the Rim With Conventional Grease

How to Properly Install the Filter on the Bike

Once the air filter has been prepared for re-installation as outlined above, and the sealing flange of the air box is clean, be sure to inspect the intake tract to ensure there are no foreign particles (dirt) in the intake, then reinstall the filter, securing the filter with the through bolt or retaining clip, while ensuring the locator(s) on the filter cage are properly indexed to the air box, as it is possible for a filter to be installed, but not sealed to the air box properly, which is critical, and an improperly installed air filter will allow the engine to draw in unfiltered air between the air filter and air box, often resulting in piston and cylinder wall scoring, among other engine damage.

How To Clean and Oil A Pleated Type Filter

Picture of A Pleated Air Filter On A Dirt Bike

Servicing of a pleated air filter requires a different technique than that of a foam filter, although during the cleaning and service of a pleated motorcycle air filter, it's advisable to follow our same recommendations concerning removal and reinstallation of the filter, which covers inspection of the filter element before cleaning, and inspection of the air box and intake tract for any dirt or particles which may have been introduced into the intake tract.

Furthermore, there are specific cleaners for use on pleated air filters which will safely dissolve oil designed for pleated air filters without harming the filter's materials, rendering the filter useless, and using any other chemicals or cleaners on the filter is likely to damage the filtering material, compromising it's filtration abilities, and potentially allowing filter particles, dirt and unfiltered air to be drawn into the air stream, which greatly accelerates the wear of internal engine parts, and often causes carburetion or fuel injection problems, none of which are any fun.

How to Clean A Pleated Motorcycle Air Filter

As mentioned previously, the cleaning of a pleated air filter requires a cleaner designed specifically for use on pleated air filters, and cleaning one of these is best accomplished by first using moderate pressure from a water hose to remove any heavy accumulation of dirt from the air filter pleats (if necessary), followed by applying the filter cleaner and allowing it to soak in for a few seconds, then rinsing the filter with water from the inside outward, continuing this process until the filter appears clean, but be sure to allow a pleated filter to dry naturally before continuing, and Do NOT Use Compressed Air to dry the filter, otherwise damage to the filter medium is possible.

How to Apply Filter Oil to A Pleated Air Filter

After you've cleaned the filter and it's been allowed to dry completely, it will need to be oiled so it can trap dirt and fine particles, making them unable to pass through the element, and it is critical that you use an oil designed specifically for use on pleated motorcycle air filters, otherwise you'll ruin the filter by using an incompatible oil which will not not allow you to clean the filter at a later date due to the cleaner that is required, and the oil that was used being incompatible.

With the proper filter oil designed for pleated air filters, apply the oil across the air filter's pleats, covering the outer surface of the filter element uniformly. If using the aerosol, you can essentially paint the air filter until the element is uniformly covered. However, If using the oil in liquid form, apply the filter oil to the peak of each pleat on the outside of the element, allowing the oil time to soak in, applying more as necessary until a uniform coverage of all pleats is achieved.

How to Extend the Time Between Filter Cleaning's

We ride also, therefore we know how much of a hassle it can to find a nasty looking air filter under the seat, but lucky for you we've come up with some ideas you'll love that'll extend the time between filter cleaning's:

  • Storing your pre-oiled spare air filters in gallon size zip lock freezer bags keeps 'em clean and fresh until you need them.

    Purchase more than 1 new filter (A total of 3 is ideal) and swap out filters with a new, clean filter, pre-oiled (By You), then wash and oil all 3 together when you have dirtied them all. Additionally, when you're swapping air filters be sure to exercise care during removal and reinstallation of the air filter, as well as while cleaning the sealing flange on the air box, and always inspect the air tract for any dirt or other particles before installing a fresh filter.
  • To further minimize filter cleaning's you can purchase filter skins, or filter covers and keep these over the filter on the dirt bike, but don't only swap out filter skins or covers with the idea of never servicing the filter, as the underlying air filter will still get dirty, as well as swapping out filter skins or covers may disturb the filter enough to allow dirt or other particles to find their way through the primary filter into the intake tract, allowing dirt or other abrasive particles to be drawn in, potentially causing carburetor or fuel injection problems, and accelerating the wear of internal engine parts.



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