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How to Clean and Maintain Motorcycle Air Filters

>> Ashley Benson

In order to work properly, a combustion engine needs air to fuel its fire. Literally. But any person with allergies will tell you that the air is packed with things that can make it difficult to breath. And just as we have our own little filter system to clean out the air we breathe (mmm... mucus), motorcycles have their air filters. The air filter on a motorcycle will vary depending on the model and make but there are a few facts about filters that remain the same across the board: there are three main kinds of filters, they all need to be cleaned or replaced and without one, or with a dirty one, your engine just won't run properly.

Types of Filters

There are three main types of filters. Sure there are variations of each and "newly improved" ones come out every day. But the basic things you need to know are the differences between a paper filter, a foam filter and a cotton filter.

Paper Filters

It seems like most street motorcycles come stock with a paper filter like any of these Bmc Replacement Motorcycle Air Filters. Whether or not this is a good or bad thing is debatable. Many people like paper filters because they are inexpensive and disposable. There is no cleaning involved whatsoever. In fact, you CAN'T clean them. Trying to clean a paper filter will just break it down and make it hard for air to get through it which will lead to some serious engine suffocation. On the other hand, many people believe that these types of filters fail to actually remove a whole lot of the particulates from the air that you don't want entering your engine. If you've joined that club, it would probably be better to spend the extra money on either a cloth or a foam filter.

Foam Filters

Foam filters such as these Twin Air Air Filters are still fairly inexpensive in the filter market and typically are stock in off-road bikes. Plus the fact that they can be reused up to a certain point makes them pretty cheap. Instead of replacing your foam filter with a new one every time your motorcycle engine needs a good breath of fresh air, foam filters can be cleaned. If you notice that it has any tears or seems to be disintegrating due to time and use, chuck it and get a new one. These things won't last forever but they'll certainly last a whole lot longer than a paper filter. There seems to be a bit of debate about how well these filters function as well. While paper filters seem to be accused of not blocking enough particulates, foam filters have been said to not allow enough air flow especially as they get dirty. Foam filters are indeed denser which means that they do let less air in. It's questionable how much less than the necessary air flow it lacks though.

Cotton Filters

The last option is, by far, the more expensive of the choices but there's a reason for that. With a cotton filter like this K&N Universal Round Straight Clamp-on Motorcycle Air Filter, you get a whole lot longer life out of them. If a cotton filter is properly maintained, you will save money in the long run over having to constantly replace the other types of filters. These filters are also known to give your engine the best performance. They allow plenty of air flow while still keeping out the harmful crap in the air. And cotton is the fabric of life after all. But this does mean that you'll be cleaning your filter every single time it starts to get a little backed up which eliminates those days when you're feeling particularly lazy and just want to throw it in the bin and slap on a new one. And cleaning a cotton filter tends to be a bit more complicated than its counterparts. Some will require a special cleaning fluid and oil in order to stay at their peak. Luckily, most filter manufacturers have been nice enough to make kits of all of the right cleaners exactly for this purpose. We love the kits that have a dye in their oil that makes it easy to see if you've sprayed all of the nooks and crannies of the filter fabric.

Checking and Cleaning Filters

It's a good habit to check your air filter every time you change your oil or (particularly with off-road bikes) after a really dirty ride to see if it's in need of a replacement or a good scrub down. As mentioned before, a paper filer will just get tossed and replaced if it's looking a little out of sorts. If a foam filter has managed to hold its own and shows no sign of damage or deterioration, it can be washed, re-oiled and put back. It's important to do this the right way, however, or you'll risk damaging the filter or making it completely ineffective.

Foam Filters

To clean a foam filter, remove it from its housing (if you're not sure where it is located or how to remove it, check with your service manual as each bike varies). Once you have the air filter removed, we recommend blocking the air inlet with a cover in order to keep that sneaky debris or dust from creeping into your engine while you're cleaning the filter.

In order to properly clean foam filters, it's important to use the correct chemicals. Using a chemical that is corrosive can break down the glue that holds the filter together. Using a chemical that is too heavy to clean it will clog the holes and pores of the foam, which will block air from flowing freely through and suffocate your engine. Getting the picture? Luckily, filter manufacturers have managed to put out some really good cleaners and oils and have been nice enough to put them in little kits like this Motorex Air Cleaning Kit so that you don't have to worry about forgetting anything.

Once you've got the dirty foam filter free from the housing, slap on a pair of these Nitrile Worx Performance Gloves and knock the loose dirt and crud free from the filter; then apply the air filter cleaner. Once your filter is fully saturated, massage it in thoroughly. Avoid wringing or stretching the filter as they are easy to rip or damage. A good gentle kneading will do just fine. Once the cleaner has worked its magic, rinse the filter from the inside out with warm water.

But don't stop there; you're not done washing it yet. Fill up a wash bucket or tub with warm water and a mild soap such as dish soap. "Why did I use a filter cleaner first and not just go straight to the dish soap step?" Mild soaps such as dish soap are safe to use on foam filters but will not be strong enough to get out the majority of the grime that's been lodged in the foam. In order to get any residual dirt out after you've used the foam cleaner, wash the filter in the soap and water solution, rinse and repeat three times. This should clean out any remaining debris and filter cleaner residue.

When the filter is back to the color is was when you first put it in your bike and your soap water is the color of an MX track after a good, long rain, gently squeeze out the excess water. Still refrain from wringing out or stretching the filter. Damaging it and having to buy a new one will only completely defeat the purpose of cleaning it. With the excess water back in the wash tub, set your filter aside to dry. Depending on the heat of the room or where you set it (in the sun vs. in a dark damp place) let the filter take as long as it needs to fully dry. You won't want any water to be trapped in the filter when you go to oil it as the oil will only trap the moisture in the filter which will then cause it to wreak havoc on your engine after you put it back. If you have an air compressor, you may use it to gently blow off excess water to make the drying process go faster. While you wait for your filter to dry is a perfect time to clean out your airbox, or filter housing, with some contact cleaner like the Maxima Contact Cleaner

Once the filter is COMPLETELY dry, check to make sure the airbox is clean. If it is, you can begin to saturate the filter with fresh filter oil. Be sure to get the entire filter including the sealing flange and lip. Then squeeze out the excess as it will make it hard for air to flow through the filter. We also recommend applying a fair amount of some sealing grease to the sealing flange before popping it back into its housing. You can use bearing grease but we love to use this K&N Sealing Grease or some No Toil Rim Grease. After that, you'll be good to go!

And of course, here is Steve Matthes to help in case you're more of a visual learner!

Cotton Filters

Just as with cleaning a foam filter, it is important to use the right chemicals to clean a cotton filter so make sure that you're fully stocked up on them or grab some from's Air Filter Maintenance Motorcycle Chemicals Section before you get started. If you're all good to go on the cleaner front, pull the filter from its housing (once again, if you're not sure where this is located or how to properly do this, check with your handy service manual). Knock the excess debris and throw on some of the work gloves.

With the appropriate filter cleaner, apply liberally and let it do its magic for a few minutes (no kneading needed). Once its had a chance to break down most of the dirt and grime, rinse the cleaner off from the inside out to help the dirt and cleaner make its way back out of the layers of the cotton fibers. With the worst of the muck free from the filter, you can now move on to washing the filter with a more mild solution. Fill a bucket or wash tub with warm water and a mild soap and swish the filter gentle around in it to clean out any remaining dirt and filter cleaner. Rinse and repeat.

With the filter now free from dirt, imagine an Italian pizza maker tossing dough in the air to flatten it out. No, we don't suggest that you put down your filter and go make a pizza. But the principle behind pizza dough tossing is one of the best ways to knock of excess water from a cotton filter. Rather than trying to squeeze out any excess water like you would a foam filter, toss the cotton filter up into the air with a bit of a spin to it. This motion will push the water from the inner layers of the filter fabric and knock it out of the filter. Do not, we repeat, do not use a compressor to try and blow out the excess moisture. Using a compressor on a cotton filter will separate the layers of the fabric and make less effective. And since you spent all of that money getting a cotton filter so that it would both last longer and give you better results, ruining it is the last thing that you want to do. Instead, with the excess spun off, set your filter aside and take a break to go make that pizza you were just thinking about. Just as with a foam filter, you'll want to give a cotton filter as long as it needs to COMPLETELY dry as you won't want any moisture getting trapped in it when you oil it and put it back on your engine.

Once you're done with your pizza and the filter is dry, apply fresh air filter oil. We recommend using this K&N Air Filter Oil. When doing this, use one from an aerosol can rather than from a squeeze applicator in order to get an even application. If using a K&N filter, also install a layer of outerwear over the filter to give it that extra bit of protection. Wipe any excess oil from the filter and put it back in its housing.

Air filters are an important part of a motorcycle engine but are often overlooked. In order to avoid giving your ride motorcycle-emphysema, be sure to check your filter as often as you change your oil. If you're doing a lot of off-road riding or ride in very dusty conditions, you should always check your air filter after every ride. With some off-road riding, you may also want to always pack an extra air-filter in case your filter gets excessively dirty in the middle of a ride and needs to be switched out before you are able to clean it. Place a clean air filter in an airtight bag and pack it with the rest of your riding gear. Riding with a dirty or damaged filter or even riding with no air filter at all will only cause unnecessary wear and tear on your engine.

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Monday, October 31, 2011 12:15:29 PM
Ross Kiihn said:

I am told that foam filters require a different oil than cotton filters. Does K & N Air Filter Oil work on all? Is it available at an auto parts store? If not, what is the price?


Saturday, February 11, 2012 6:38:09 AM
Buck Harris said:

I see that I've been making some mistakes in cleaning my foam filters. After reading your info I will improve my techniques and enjoy my KLR 650 longer. Thanks.


Saturday, February 11, 2012 5:46:36 AM
ken said:

Very good I hope more tutorials like this are offered in the future


Saturday, February 11, 2012 7:23:14 AM
Fernando said:

great post, its good to know the importance of the maintaining the air filter


Saturday, February 11, 2012 10:15:17 AM
Rob Iwen said:

great stuff.thx


Monday, February 13, 2012 8:35:47 AM
Jimmy said:

My K&N filter was installed by a shop. I have never really understood the steps required to maintain the filter. Thank you for the great explanation! is the web's largest powersports store with more than 8 million factory fresh motorcycle parts, apparel, accessories and more online, including motorcycle helmets, motorcycle boots, motorcycle gloves and more.