Be sure to regularly sharpen rotary mower blades, which operate on the principle of a sickle. Shredded or brown tips of grass blades is 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 which end of 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.