The importance of a clean air filter.
Your lawnmower engine needs air to mix with the gasoline vapor to create the internal explosion that drives the motor. All this is controlled by the carburetor. The amount of gas used is controlled by the throttle valve that you can often manually adjust at the speed controls on the handle. The amount of air used is determine by the internal vacuum caused by the piston moving down in the cylinder. It creates a vacuum that draws in the Air/Fuel Vapor mixture before compressing it for the spark plug to ignite and produce the power stroke that drives the engine. So old gas that doesn't vaporize well or a air filter that is dirty will affect how well the engine can suck in the proper Air/Fuel Vapor. This is why a clean air filter and fresh gas are so important to a clean running engine. You are probably getting fresh gas for your engine as you use it up but are you checking your air filter?
Air filters come in two popular forms; paper and foam.The term "paper" is somewhat misleading, as the filter's material is considerably different from papers used for writing or packaging, etc. Paper filters do a great job of blocking dirt particles from getting into the engine until they become significantly clogged with dirt. At that point they need to be replaced. Typically you can hold them up to the sunlight and if you can clearly see light passing through, then its fine. But if you see sections blocked from light then the air filter needs to be replaced.
Foam filters are actually oil-wetted polyurethane foam elements. Foam was in the past widely used in air cleaners on small engines on lawnmowers and other power equipment, but automotive-type paper filter elements have become more popular. Depending on the grade and thickness of foam employed, an oil-wetted foam filter element can offer very high dirt capacity. The advantage is that foam filters can be washed clean with soap and water and when dry have a light coating of engine oil soaked in to make them catch and hold the dirt better. The light trick doesn't work as well for the foam filter but if the surface looks dirty, a quick wash job and a little oil does the trick quite well.
And when you are ready to replace your oil filter check out our air filter selection here at MrMowerparts.com