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Outside of filter covered with oil
It seems that everyone has their own way of taking care of the air filter on their noble stead. However, you’d be surprised by how many people do such a simple task the wrong way. Now, I’m not saying there is only one way to oil an air filter correctly, but there are a dozen different ways to screw it up. Here I’ll go through and explain how to oil an air filter in a way that has been tried and tested for decades.

Things you will need:

Air Filter Maintenance Materials

1. Air Filter
2. Foam Filter oil
3. Pair of elastic gloves
4. Quarter bucket (catch can for access oil)
5. Brake Parts Cleaner or WD-40
6. Rag(s)

Step 1: Turn Filter Inside-Out

Motocross Bike Air Filter

First, you want to turn your filter inside-out. By doing this you give the inside of your filter more of an opening to get every spot possible. As we all know, un-oiled sections of an air filter will allow dust, sand, and other debris to bypass the foam and work itself into carbs, injectors, or ever worse, the engine.  

Step 2: Evenly Oil the Inside of the Filter

Oil the Inside of Filter First

Now you can start oiling. When you start to pour your oil, make sure you are working your way around the filter. It doesn’t help if you put a lot in a little spot. The idea is to get every inch of the foam coated in oil. If it makes things easier, have someone pour the oil slowly while you turn your filter. Once you work the oil in the foam the inside should look like the picture above.
No spots, evenly oiled.

Step 3: Flip Filter Right-side Out

Outside of filter covered with oil

After the inside of the filter has oil throughout the foam, you can now turn your filter right-side out (the correct way). If you worked your oil in well, the outside of the filter should be a spotty blue (or the color of your foam filter oil). Do the same thing as you did on the inside. After you get done your outside should look like this. 

Step 4: Sealing the Air Filter

Grease the Air Filter Rim

I personally do not put grease around the ring of my filter. Greasing the rim of air filters became popular decades ago, when filters and filter cages didn’t quite create a good seal. These days, most bikes come with better performing airboxes and don’t require grease. If you opt out of using grease like me, you need to make sure you have air filter oil all the way around the rim of the filter. This is important as well because dirt seems to sneak by if your not careful. Owners of KTM’s should take extra precaution, as the airbox/cage design can be tricky to get a proper seal. Triple checking that you have good contact all the way around the filter during installation is crucial for prolonged engine wear.

Once you have carried out these steps, you have successfully oiled an air filter. Make sure you don’t have to much oil applied causing your bike to load up from lack of air. The filter should not be saturated with oil. A light, even coat is key.
Why do we oil air filters inside to out? Because with this method you are able to work oil into the filter, rather than just placing the oil on top, giving you better protection from the elements.

Author: Jesse Ansley