Air filters

The air filters on Harley-Davidson have changed quite a bit over the years: it has been a long way from the air horns of the early days, which only had the task of keeping out splash water or supplying preheated air through the cylinder cooling fins, to the voluminous air filter boxes of the current models, which not only filter but also dampen intake noise.

What does an air filter do?

One of its main tasks - the name says it all - is to filter the air sucked in by the engine. Dirt and water disrupt the function of the carburetor and cause damage inside the engine. The filter media used in the air filter element include wire mesh, cotton gauze, foam or paper. With the exception of the paper filters, all are additionally moistened with air filter oil in order to capture even very fine particles. The air flow to the carburetor is influenced by the air filter housing. The temperature of the intake air is decisive for the performance of the engine, so the intake opening of the air filter is designed accordingly.

Do you have to clean air filters? How often should air filters be cleaned or replaced?

The intervals for checking the air filter element are specified in the manual for the original replacement filters. During the check, you decide whether cleaning is sufficient or replacement is necessary. Paper air filters can be blown out, all other air filters should be washed out and freshly oiled. K&N air filters should be cleaned every 20,000 km; they only need to be replaced if they are damaged.

What are intake funnels for?

Air filters create a certain resistance to the air. Wherever you want to avoid this resistance completely, you rather use intake funnels, especially in drag racing. However, if dust swirls up and stones splatter, you might prefer try to optimize the airbox.