Small engines are gasoline-powered internal combustion engines typically producing less than 25 horsepower. They power a wide range of homestead equipment including lawn mowers, string trimmers, chainsaws, tillers, generators, water pumps, and pressure washers. Most small engines are four-stroke or two-stroke designs. Understanding their operation and maintenance significantly reduces downtime and repair costs.
Four-stroke engines are the most common type on homestead equipment, used in mowers, generators, tillers, pressure washers, and water pumps. They operate on the Otto cycle with intake, compression, power, and exhaust strokes. Fuel is stored in a separate tank, and engine oil is stored in the crankcase. Common manufacturers include Briggs & Stratton, Honda, Kohler, and Kawasaki.
Two-stroke engines are used in handheld equipment such as chainsaws, string trimmers, leaf blowers, and hedge trimmers. They are lighter and more powerful for their weight than four-stroke engines but are less fuel-efficient and produce more emissions. Two-stroke engines require fuel premixed with two-stroke oil at a specified ratio, typically 50:1 or 40:1.
Regular maintenance is the primary factor in small engine lifespan. Oil changes are required every 25 to 50 hours of operation for four-stroke engines. Air filters must be cleaned or replaced. Spark plugs are replaced annually. Fuel stabilizer prevents carburetor gumming during storage. At the end of each season, fuel should be drained or treated to prevent ethanol-related damage.
Most small engine starting problems are caused by stale fuel, a dirty carburetor, or a bad spark plug. Non-starting engines should be checked in order: fuel supply, spark, compression, and air filter.