more... > Commercial Horticulture > Equipment > Small Engines > Centrifugal Clutches for Small Engines [Image: Centrifugal clutch on string trimmer] Centrifugal clutches are common on many grounds maintenance machines including string trimmers, chain saws, and some lawn mowers. Engine Oil for Lawn and Garden Equipment [Image: API symbol] Oil is the lifeblood of any engine. Neglecting your oil can be a costly mistake. 2-Stroke and 4-Stroke Engines [Image: 2-stroke engine on string trimmer] Most small, hand-carried lawn and garden tools use 2-stroke engines and most larger machines such as lawn and garden tractors use 4-stroke engines. The reason for this has to do with the weight ratio of the engines. Oil and Fuel Filters for Small Engines [Image: external fuel filter] One of the most important things you can do to maintain your small engines and tractors is to service the oil and fuel filters as needed.  more articles... Preparing Small Engines For Storage [Image: Installing sparkplug with torque wrench] There are some simple steps you can take before storage to make your equipment easier to start when you need it again. Rescue Your Lawnmower or Other Small Engine After a Flood Many lawnmowers, string trimmers, leaf blowers, and other lawn and garden equipment with small engines were inundated during the flooding from hurricanes Katrina and Rita. In many cases, that equipment can be salvaged. Air Filters for Small Engines [Image: primary filter] One of the most important things you can do to maintain your small engines is to service the air filters as needed. What Is Your Spark Plug Trying to Tell You? Carefull examination of the spark plug(s) can yield insights into other maintenance needs on your engine. Safe Handling of Gasoline [Image: gasoline can on ground with nozzle touching can] One of the most hazardous substances most of us have to deal with is gasoline. We tend to take it for granted since it is so common and familiar, but we should pay it more respect. How To Choose a Lawn/Garden Tractor - Engines [Image: vertical shaft engine] One of the factors that most affects both the capability of a lawn/garden tractor, and the price, is the engine. Lawn & Garden Equipment Engines With Reduced Emissions The EPA found that small spark-ignition engines of 25 hp or less contribute about 20 percent of hydrocarbon emissions and 23 percent of carbon monoxide emissions from all mobile sources. As a result of this perceived problem, the EPA has issued new regulations on small engines.