Function of air filter
1) The function of the air filter is to filter out the magazine and sand particles in the air to reduce the wear of the cylinder and piston ring and extend the service life of the engine;
2) Eliminate the noise of certain intensity produced by the engine during the suction stroke.

The air filter can be divided into three categories according to different methods of filtering impurities:
(1) Filter type, which uses air flow to pass through narrow and tortuous filter element channels such as metal mesh, metal wire, fiber, microporous filter paper, etc. to produce multiple contact, causing dust to be stuck on the filter element. It is most effective for removing small particles.
(2) Oil bath type means that before the air enters the filter element, it stays over the oil surface at the air flow direction, so that large particles are stuck due to inertia thrown to the liquid surface.
(3) Inertia type, which uses the air flow to change the flow direction rapidly, so that the dust has a large inertia and is removed. It is effective to remove larger particles. Before passing through the filter element, the air is separated by progressiveness inertia, and 50%~60% of coarse particles are removed, and then fine filtered through the paper filter element.

Long-term use of the air filter will cause gas blockage, which will cause additional resistance to the air intake of the engine, and reduce the inflation volume and engine power of the engine.
Therefore, the selection of appropriate air filter is the premise to ensure the normal operation of the engine. At the same time, it can effectively reduce the early wear of relevant engine parts, extend the service life of the engine, and also reduce the use cost of users, so that customers can get the greatest benefits.
The air filter shall be reasonably selected according to the filtration effect and the suction capacity of the engine. The original resistance of the oil bath filter is less than 980Pa for small power engines and more than 980Pa for medium engines. With the increase of time, the resistance can increase to 2900Pa. The original resistance of the paper filter element is not more than 390Pa, but the resistance may increase sharply by 3900Pa~5900Pa after scaling. Pay attention to regular cleaning and maintenance during use to avoid excessive resistance, especially the paper filter element should be replaced in time.