Most dual-sport and enduro motorbikes have resusable foam airfilters. Whether you are riding on the road or off-road in Spain, the climate is so dusty here, you will need to clean your foam airfilter regularly. Over the years, i’ve tried many different products for cleaning my airfilters, and whilst it may be controversial, this method produced the cleanest foam filters. This process should be done outside or in a well ventilated area.
I always have two foam airfilters for every bike, this way you can clean the dirty one when it suits you, and it helps during this first stage. They only cost €15, which is half a tank of fuel for my KTM 640 Adventure, so its hardly going to break the bank. Remove your dirty airfilter, and immediately replace it with your clean and oiled spare filter. If you haven’t got a spare airfilter, you should block the air-inlet with a clean cloth or a piece of sponge. If you are using a clean cloth, thoroughly shake it first to discard any fibres or particles so they don’t all into the inlet pipe.
Find a clean bowl, or do what I do which is to cut a 5 litre water bottle in half, and some oil resistant gloves (having worked as a mechanic for decades, i simply use my hands). Place the airfilter into the bowl dirty side facing down, and then pour clean petrol into the middle of the airfilter until the filter is half submerged in the petrol. Quickly, squeeze the filter in the petrol to wash away the dirt and filter oil. When the petrol becomes discoloured, pour it into an old recepticle. The petrol will evaporate leaving behind the dirt from the airfilter so it doesn’t need to be a clean container. Repeat this process until the petrol remains clean. Don’t leave your airfilter soaking in the petrol, the squeezing/washing of the foam filter each time should only take a few seconds before the petrol is dirty or you can see that it has remained clean. Once the filter is clean, give it a good shake to remove any excess petrol and leave it to dry. It doesn’t take long for the petrol to evaporate from the filter, and then you can apply a fresh coat of airfilter oil. Personally, I prefer to use a spray oil. I apply it in a lattice spray patern across the filter. Once sprayed, you can either refit the filter to your bike, or place it in a clean, sealed plastic bag so it is ready to fit when you need to change the filter.
I know there are some bio airfilter oils available now, which are washable in water, but I haven’t had the chance to try them. If any of the manufacturers want to send me some to review, contact me via the website.