Air cleaners are a real necessity for a long engine life as any dirt will certainly ruin an engine. Most motorcycle air cleaner filters are one of three types: oiled foam, oiled fabric and dry paper.
Oiled foam is very popular with dirt bikes. On oiled foam filters the real filter is the oil. The foam is only a support for the oil. To clean them, rinse in solvent several times or until clean. Then ring them out, and let them dry. Lastly, put on a fair amount of oil and work the oil into the foam with your hands. Special air filter oil is available for this application.
Fabric filters, have a surgical type of fabric inside a metal mesh. They work very well and seem to flow a lot of air. They use a special oil you get from the air filter maker (K&N). Clean them with soap and water, let dry, and then re-oil. With care, they last quite a while.
Paper filter are used on a lot of street motorcycles. They work effectively when new and clean. If they get wet, they stop passing air. When they dry out, they usually start working again, but don't flow air as well as before getting wet. The water seems to stick the paper fibers together hindering the air flow. If the bike has been sitting a long time, the paper filters absorb water from the air and this starts to plug them up. While you can clean them somewhat by blowing with compressed air the only real way to clean them is to replace them with a new one.
We stock and fit BMC, Twinair and Unifilter air filters.