Power to the People Who Keep Up Their Gas Engines

Small gasoline engines power many common yard tools. And you don’t have to be a mechanic to keep a small engine running smoothly, whether it’s a two-cycle engine, used on chain saws and other light machines, or a four-cycle engine used on heavier equipment such as lawn mowers and tillers.

The Basics

To plan for proper maintenance, there’s no substitute for reading the owner’s manual. It’s the best way to become familiar with a particular machine’s parts and how it works.

To keep track of how much you use a machine, put a strip of masking tape on the housing and log on it the operating hours. Or just estimate the yearly use of the machine and mark on a calendar the dates you should service it.

Every time you service an engine, check the mounting bolts; loose ones can cause excessive engine vibration. Also make sure that any knobs, levers or brackets are secure.

Before Use

Clean grass and debris from the air-intake screen, muffler, oil filter and governor-linkage areas with a stiff plastic-bristle brush. Remove the air-intake screen to clean the flywheel fins.

Check the oil level in a four-cycle engine. (Oil is mixed with gasoline in two-cycle engines.) If there is no dipstick, open the oil-filler cap. Check that the oil reaches the opening or is even with the top of the slot. Add oil if necessary.

Every 25 Hours of Use

Change the oil in a four-cycle engine. Drain the old oil into a container by removing the drain plug on the bottom of the engine. If there is no plug, tip the machine on its side and pour out the old oil through the filler hole. Refill with new oil. Dispose of the old oil at a recycling center.

Lubricate exposed cable and pivot points of any control levers, such as the clutch and throttle controls. Use a few drops of light oil, white lithium grease or a spray silicon lubricant.

Also clean or replace the air filter regularly--as your owner’s manual recommends. Change it more frequently if you use the machine in dusty conditions. Tap a paper air filter on a hard surface to release dirt. Wash and oil a foam filter as directed.

After 50 Hours of Use

Check the sparkplug. Remove it with a sparkplug wrench, keeping the socket squarely on the plug to avoid cracking it.

Clean the plug with solvent and a wire brush. Replace it if the electrodes are rounded or the ceramic insulator is cracked. Before reinstalling the plug, check the gap between the electrodes, following the owner’s manual specifications. Use an inexpensive feeler gauge, available in hardware stores. The gauge should slip between the electrodes with a slight drag. Adjust the gap if necessary. If you’re in doubt about a plug’s condition, install a new one.