Most homeowners have a rotary-type lawn mower that requires periodic maintenance to keep it working efficiently and safely. Use the operating and service instruction manual provided with your mower, and consistently perform the suggested maintenance.
Basic engine maintenance is essential. Use the gasoline and oil recommended by the manufacturer. When working on the mower, be sure the blade and all moving parts have stopped. When accessing the underside of the mower for inspection or cleaning, always turn it so that the air-filter side of the mower is up. Otherwise, the oil will drain out into the air filter and the engine won’t start. Also, detach the spark-plug wire so the engine won’t start accidentally. Keep spark plugs clean and have an expert adjust the carburetor. Check air filters regularly and clean or replace them when dirty.
Be sure to regularly sharpen rotary mower blades. It’s advisable to have an extra blade on hand so a replacement is available when you detect poor cutting. Shredded or brown tips of grass blades are an indication of a dull or damaged mower blade. You can sharpen rotary mower blades with a grinding wheel and file, but be careful not to destroy the balance. To determine if the mower blade is out of balance, put a nail in the wall and hang the blade from the hole in the center of the blade. File more off the blade on the heavy end.
Excess vibration is an indication of a damaged blade, mounting, or crankshaft. Frequently tighten the blade and engine mounting bolts, as well as any other nuts, bolts, and screws. Check mower wheels, bearings, and axles for wear and lubrication. If there are grease fittings, check them every couple of months. Replace loose, wobbly wheels. Be sure to keep the drive mechanism on self-propelled mowers in good working order. Check belts and gears for wear and fit.
After each use, clean the underside of the mower with a strong stream of water. The metal deck can rust out if residue builds up. To reduce fire hazard, keep the engine free of grass, leaves, and excessive grease. Check the grass-catcher bag for wear or deterioration, and replace when necessary. At the end of the mowing season, be sure to drain the gas and follow the winterizing instructions in your owner’s manual.
Source: CSU Extension