Air Filter Maintenance How to clean your air filter and why you should

Riding our bikes is fun; working on them doing preventative maintenance isn’t always as fun so it’s often neglected.  One area often neglected is also one of the most important, your air filter.

Having a clean, properly oiled air filter is important for two reasons.  First, dust and dirt getting into your bikes engine will dramatically increase wear of the piston and rings.  Second, a clogged air filter (from dirt or improper oiling) will starve your bike for air making it run poorly.

When I had my first bike back in 1975, we used gasoline or other solvents to clean the filter and motor oil to oil them.  We also typically ran some grease around the filter lip to aid sealing.  Then came specialty air filter oils that were tackier than motor oil, but still required solvents to clean.  These solvents eventually would degenerate the foam of the filter.

Today, we have environmentally friendly cleaners and oils to choose from.  For this thread I used the No-Toil system which I have been using for two years now and feel it does a great job and is easy to clean up, requiring just their cleaner and water.  Use what ever you like and works for you!

For the following examples, I used my son’s 2006 YZ-85 after an afternoon at our local track.  Figure 1 Fig1 shows the filter I took out of my son’s YZ-85 after about 3 hours of on-track time.  Compare this to Figure 2 Fig2 which shows a clean, but not oiled Twin-Air filter.  Yuck!  After removing the filter, I recommend using one of the commercially available air box covers to keep and dirt or other objects from going down the air inlet.  Figure 3 Fig3 shows a Twin-Air unit in place after taking out the air filter.  An additional benefit is that you can then wash the inside of the air box when washing the bike and not get water down the intake.

With No-Toil you simply put their cleaner into some warm water (a bucket, wash tub, or even a wash machine works well), place the filter (s) in, and work the cleaner in (and dirt out).  Figure 4 Fig4 shows my wash tub before cleaning the filter, and figure 5 Fig5 shows it after (notice how much dirt the filter was holding!).

I then rinse the filter using warm water and allow it to dry.  Once dry its time to oil the filter.  With the No-Toil (or really any other filter oil) you want to get the filter thoroughly saturated with filter oil, and then get as much as you can back out.  If you leave too much oil in it, it will restrict the air flow and your bike will run poorly.  Too little and it may let dust past which will cause premature wear of your engine.  Wearing rubber gloves, after saturating the filter and working the filter oil through the filter, I then squeeze as much as I can back out (do not twist or wring the filter as it can rip or tear).  I then stuff the filter with some paper towels and squeeze them again to let the paper towels absorb any oil that comes out.  On the Twin-Airs, they take on a reddish tint when oiled correctly as shown in figure 6Fig6.

The next step is optional, but I prefer to run a bead of air filter grease (No-Toil again) around the air filter lip and mounting bolt hole.  At worst it just takes a few more minutes and at best it provides some additional sealing protection.  Figure 7 Fig7 shows the grease around the lip.

Figure 8 Fig8 shows the freshly oiled filter back in place on the YZ ready for the next outing.  In extremely dusty conditions, I will prepare an extra filter for my son’s and my bike and put them in plastic bags, ready for use during the day if the original gets too dirty.  Figure 9 Fig9 shows them all sealed and ready.

Also (added 06/14/2007), when you wash the filters check them to make sure there aren't any seams opening up or tears/holes that could let dirt through.

So, thats how I do it.  Feel free to add your own ways of doing air filter maintenance!  
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Dave H 2006 YZ250
(2008 YZ 125 son)

You should have let the dirt settle after washing, and then let the water drain and then taken a picture of how much fine dirt actually comes out of the filters. Doing three at once you can imagine how much dirt collects at the bottom of our sink in the garage.

Nice tutorial Dave. Its amazing how clean the filters come out after being so filthy. I never saw a filter come out that nice before using no-toil.  

You are right; I'll take one after this weeks riding.  You can start a garden in the dirt settled on the bottom as the water drains out!  
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Dave H 2006 YZ250
(2008 YZ 125 son)

Great post Dave. I always recomend No Toil also as you know. And really can't stress enough the importence of clean air going to the engine. But can be one of the most negglected do to it being a pain in the butt. I like no toil because even doing 2 at once, The sink isn't full of oil and the place smelling like break cleaner. Witch you need just to get the oil out of the sink when your done! Also doing a few at one time is great and just put the fresh ones in a air tight bag. And also letting the filter DRY COMPLEATLY is mando. before oiling. I use a hair dryer LOL. You don't want water in your engine. My 2 cents.  
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DIABETES SUX!

Supposedly using your washing machine is even easier; but my wife isn't game to that, so I use the wash tub.

I also use the time after they are washed to inspect the filter.  I should add that as a last step. (I think I will).  
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Dave H 2006 YZ250
(2008 YZ 125 son)

Dont forget the PJ1 cleaner and oils. I have outstanding results with both products  

I also use PJ1 cleaner and oils  works very well for me. I have to clean my airfilter alot i mean i know its good to do it alot but with my airbox opened up it gets dirty very quickly. One time I found a huge piece of bark in it like 4 inches long and im still trying to figure out how that got in there!!  
2006 YZ250

anyone try using just a mild  dish soap?Would that work or how would it hurt?  

Mild dish soap doesn't break down the oils like a dedicated cleaner does.  

Bill H.
Temperance, Mi
2000 CR250R
1991 YZ125

Hey, Does anyone know who makes the best Air Filters for the money if you can not spend the BIG BUCKS for OEM?  

Great Post. To all the 4 stroke riders this thread applies to you the most. This is the aboslute key to keep those thumpers chuggin.  
'Forgive me Lord for I have sinned; hit a 4th gear jump 5th gear pinned'

Real Men Ride Four Strokes-Always Have.

Great guide but i disagree with one part. You say running grease around the edge is optional, I think you MUST put grease in the edge. without grease espically on older more worn airfilters dirt can easy get around the edge of the filter and into your carb.  
04 CRF250X

This may be a dumb question but as long as we are on the subject.  My 2002 RM 125 has a foam filter that looks like the one DLHamblin showed in his pics above but it also has another filter liner that goes over top of it that is made out of a different material. What is the best way to clean and oil this type of filter?  Do I clean, oil, and wash both the foam filter and the liner or just the outside liner. Hope this makes sense.  

Its probably a Uni-Filter; its two seperate pieces (the Twin Air in my example is also two pieces but they glue them together so its one unit).

I haven't used a Uni-Filter, but I would clean each piece the same way and also oil both.

Any Uni-Filter users want to offer an opinion?  
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Dave H 2006 YZ250
(2008 YZ 125 son)

I use uni 2 stage on my 2T. I used to oil both inner and outer the same way. But I feel its kinda restrictive. After Many cleanings i started to notice the inside filter always as clean as the day i did it so ive really backed off on the amount of oil i use on the inside filter.
Also like Woods said when u wash your filter make
100 0/0 sure it is dry before oiling em up. water trapped in side will never dry once it is enveloped in oil. I let em dry for a least a day in the house or on my GF's pillow or somewhere its warm.