Are you looking for the right air filter size for your motorcycle? It can be a tricky task, but with a few simple steps, you can make sure you get the right size. First, measure the outer diameter of the end of the carburetor filter. This is usually done with a ruler or caliper. In the picture we show a common Mikuni of 22 mm. Next, compare a new filter to an old one to “feel” the level of dirt contamination.
If no light passes through, it means that the change should have occurred a long time ago. As a general rule, it's best to change it when you see some light, but with a much smaller amount than what you see going through a new filter. When searching for replacement air filters, start by limiting yourself to the depth of the air filter. There are thousands of sizes of air filters, and manufacturers of heating, ventilation and air conditioning systems make it as complicated as possible so you have to buy expensive replacements. To test the filter, place a workshop light inside the folds and see if you can see the light passing through it. Keep in mind: photons of light are much smaller than air molecules, and when enough dirt has accumulated in the folds of a paper filter to stop even light from passing through, it's time to change. We recommend changing your air filter at a distance of 10,000 to 15,000 miles, depending on the environment in which you are driving.
Wet an original paper filter or gauze filter and the fibers will swell, strangle the air flow, and possibly stop the engine. OEM filters are very effective at filtering particulates and protecting the engine, but they don't maximize airflow. This is an easy way to find out what size your air conditioner filter is, but not all filters have their size measurements listed. High-airflow filters are made from foam material that is oiled so that when dirty air circulates through and around the fiber filaments, the oil traps and holds the dirt. When a foam filter gets dirty enough for all of the oil to dry out, dusty air may pass through the foam and into the engine.
