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www.landscapeirrigation.com Landscape and Irrigation January/February 2017 21 Valve lash is the gap maintained between the rocker arm top and the valve stem. Most engines in production today have some form of adjustment for the air gap. As the engine accumulates hours at work and wear takes place, this gap will typically widen. This will cause lost motion from the camshaft, and since the tappet, pushrod and rocker are not following the camshaft lobe profi le as exact as possible, there will be a reduction in performance of the engine — not to mention fuel economy. Consult the engine's operator's manual or service manual for recommended service intervals, and lash settings and procedure. 3. Refresh the oil Don't forget to start the season with an oil change. Then, changing the oil every 100 hours of operation for larger equipment and every 50 hours for smaller utility pieces of equipment is paramount to operating a productive fl eet. Small air-cooled engines are especially hard on engine oils. Their oil operating temperature is often approaching 300 Fahren- heit, depending on ambient conditions. When oil is in service for longer than recommended periods of time at elevated tempera- ture during operation, it forms a tar-like substance that makes it diffi cult for the oil to lubricate, clean and cool the engine. Accord- ing to Billigen, checking, adding and changing the oil regularly is the best defense against oil breakdown and engine failure. Also, using the best oil for the engine being operated will help performance. The Society of Automotive Engineers has developed a categorization of motor oils that will indicate the viscosity (thickness) and temperature in which engine oil can be used. This is typically called the weight of the oil, which is printed on every bottle of oil. It also will indicate whether or not the oil is synthetic. Check the owner's manual for the optimal oil, but Billigen says a SAE 30 oil is typical for most engines operating in 40 degrees Fahrenheit or warmer. 4. Get some fresh air Without access to clean air, a small engine can become the subject of a dirt ingestion failure fast. The engine air fi lter should be changed every 100 to 250 hours, depending on how dirty the environment is in which the contractor is working. A clogged or old air fi lter will restrict airfl ow and adversely affect the air- fuel mixture. That will result in decreased horsepower, poor fuel economy, slow response, tough starting and, ultimately, shorter engine life if the fi lter begins to bypass. Jeff Salem is a public relations counsel at Swanson Russell, Lincoln, Neb. He can be reached at jeffs@swansonrussell.com. DON'T GO IT ALONE. BE PART OF SOMETHING BIGGER. JOIN US! 800.395.2522 | bit.ly/lanirrmag