Air Filter Cleaning

Ah, cleaning and oiling foam air filters takes me back to my dirt bike days. I haven't had a motorcycle with a foam air filter in many years now. However, my new 2016 Kawasaki KLR650 has one and, given the environment that I've been riding recently, I suspect that it may need some servicing.

The factory interval for cleaning and re-oiling the foam air filter is 7,500 miles. Although I only have 3,000 miles on the motorcycle I thought I should get a look at the air filter after last weekend's Devils Creek Rally. I was also in a rally in South Florida several weeks ago which was pretty dusty, but it seemed like I was in a dust and sand cloud for three straight days at Devil's Creek.

The air box is located under the seat and requires removal of the seat and right side panel to access the air box cover and the filter. I also removed the left cover to get access to the left side of the air box and snorkel for purposes of inspecting the air box. Removal of the cover is one bolt and the cover pops off.

The KLR650 air filter is a single-stage, reusable, foam-type air filter. The filter is not an expensive part; only $21 for the factory filter at BikeBandit and there are some aftermarket types. However, if cared for, the filter will last a good long time.

NOTE: It should be understood that it's not the foam that filters the air entering the carb/engine; rather, it's the oil that filters the air. The foam simply suspends the oil in place to do its job. Dust and dirt particles attach to the oil as they work their way through the foam. Not oiling the filter is the worst thing you can do to this system.

Although the maintenance spec on air filter cleaning/oiling is 7,500 miles, the proper interval should be consistent with the environment that the motorcycle has been used. As you can see in the next two photos, my air filter is very much due for cleaning and re-oiling after a total of only 3,000 miles.

In my case, the inside of the air box was such a mess that it required cleaning also. It was full of sand and the drain tube had water in it. I got after the box with a small brush and my shop vac and got it cleaned out...

...then I drained the water through the drain hose (see next photo). Having water in the drain hose is an issue because it means that water got into the air box. It could have come through the snorkel as we had a lot of deep water crossings in the last rally. I think it may be best to remove the drain plug in the drain hose going forward when I'm planning to do water work.

For purposes of cleaning, the Service Manual says that the filter should be soaked in a high flash-point solvent like kerosene. However, I'm not going to keep kerosene around just to clean my foam filter when there are popular foam filter cleaners, such as the UNI cleaner included in the UNI Air Filter Service Kit. In addition, I personally think a good "specific-purpose" cleaner over harsh solvents improves the overall life of the foam filter.

I always wear disposable shop gloves when performing this maintenance. I have found that both of the UNI fluids are very nasty on hands.

The UNI Cleaner is sprayed onto the filter while in a container like my pail (sometimes I use my oil drain pan) and I carefully work the cleaner into the foam with my fingers. It takes some time to get the filter clean. See my note above; I'm working all the old dirt/oil out of the foam, it doesn't just dissolve by spraying the cleaner on the foam. It's not unusual for me to have to repeat the process. It's not a process to be rushed. After the cleaner has penetrated the entire foam filter I let it sit for 5 minutes in accordance with the product's instructions and then thoroughly wash it in plain warm tap water...no soap.

Viola! That looks a lot better.

The filter needs to thoroughly dry out before it can be oiled. I do not use a hair dry, heat gun, high pressure air hose or anything similar on the filter. I don't put it in the oven or microwave, or even out in the sun. All of those actions may damage and/or shrink the material cutting its life and making it less effective as a filter. I just let it set at room temperature and go do other things until dry. My workbench fan blowing on the filter is okay. It has to be thoroughly dry before oiling!

To oil the filter, I also used a specific purpose oil. The UNI Oil in my kit was sprayed on and worked into the foam with my fingers. The foam needs to be completely and evenly saturated with the oil, but not so thick that its dripping or gobbing. I look carefully to make sure I didn't miss any spots. It's the oil that's doing the filtering so missing a spot would be a big problemo!

Once the filter was completely oiled, it could be returned to the air box with no drying time. In the case of the KLR650, the filter mounts on a cage and is one wingnut into the box. Then I do reassembly. Overall, a simple process.