Lawn Mower Maintenance

Taking care of your lawn mower will lengthen its life as well as eliminate time-consuming problems. The manufacturer’s maintenance manual is the best guide to help you keep your mower in good working order. Follow these general instructions if you don’t have an owner’s manual.

Cleaning

On push mowers, scrape away the accumulated grass with a stick or a wire brush. Hose off the mower and then wipe down each blade and all metal parts with an oily rag.

On power mowers, use a small stick to remove all grass and debris from between the cooling fins around the engine. If you don’t, the engine will overheat and damage internal parts. Then, using a clean dry rag (an oily rag will attract more dirt), wipe down the engine and the housing. Be particularly careful to clean around the oil and gas openings.

If the mower is already badly coated with oil and dirt, first wash it with hot, soapy water. Then hose it off and let it dry in the sun. Be careful not to let much water run around the spark plug—wipe it with a damp cloth instead of hosing it.

If the engine fails to start after you have washed it, remove the plug and wipe it with a clean, dry rag. Also wipe the inside of the hole. Then put a quarter-teaspoon of gasoline down the plug hole. Replace the plug and start the engine.

The underside of a power mower also needs regular cleaning, particularly when the mower is used to cut very green or damp grass. This grass will accumulate; when dry it can become as hard as cardboard, making it difficult to scrape off. On a rotary mower, the grass can also plug the blowhole for the clippings.

To clean the underside, first pull the spark plug wire free from the plug to prevent it from starting accidentally if the blade turns. Then tip the rotary mower to the side and hose off all clippings from the underside of the housing, using a power nozzle. Do not allow the engine to get wet while it is hot; however, you can spray the bottom side of the mower without spraying the engine. Then let the mower sun-dry. To prevent grass clippings from sticking, try spraying the underside with a product that prevents food from sticking to frying pans.

Sharpening

Keep the mower blades sharp. You can tell that blades need sharpening when the cut ends of grass blades look ragged, giving the lawn a white cast after mowing.

Reel mowers are best sharpened by professionals to ensure even and accurate work.

The blades of rotary mowers are easy to sharpen at home. Only a small portion at the end of the blade actually cuts the grass, so this job is easier than it seems. A dull rotary-mower blade cuts grass, but it leaves it looking ragged. In addition, it may be out of balance, which will make the mower vibrate excessively and damage the engine. If either symptom appears, remove and sharpen the blade.

To remove a rotary blade for sharpening, follow these steps:

  1. Run the tank nearly dry so that gasoline won’t spill when you tip the mower on its side.
  2. If your mower has an oil-bath filter, remove it.
  3. Always remove the spark plug to guarantee that the engine won’t start. If the spark plug wire were connected, the engine might start when you turned the blade to remove it. Tuck the wire back so it won’t fall forward and rest against the plug.
  4. With an adjustable wrench, loosen the nut holding the blade, and remove the blade. You may have to block the blade with a piece of scrap wood to keep it from turning with the wrench. Most blades have two small shear pins set in them. These keep the blade from turning under the holding nut and protect the engine. If the blade hits something unmovable, the pins shear off and the blade stops, but the engine keeps running. (If it stopped abruptly, it could be damaged.) These pins will come out when you remove the blade; be careful to keep track of them so you can return them to their proper place later on.
  5. Place the blade in a vise with the cutting edge up. Using a bastard file or a grinder, sharpen from the outer edge toward the center. Follow the existing bevel, or, if that’s gone, sharpen at a 30-degree angle. Push the file down and across the length of the cutting edge in one motion, lifting the file on the return. Then repeat. Don’t try to file away deep nicks. Instead, round them out with a small, round file. A V-shaped nick can be the start of a crack. If the blade has any cracks, discard it and buy a replacement. As you sharpen, check periodically to see that the blade remains balanced.
  6. After sharpening, check the blade for balance. The best way is to drill a hole through the exact center of a cork and put it in the blade hole. Put a slim screwdriver through the cork hole and hold it horizontally to see if the blade stays level or if one side is heavier and falls. You can also balance the blade by putting it on a nail driven in the shop wall, but the nail must be centered carefully in the hole or else you won’t get an accurate balance. If one side is heavier than the other, remove more metal from that side during sharpening.

Engine Maintenance

On all power mowers, good engine maintenance is the key to long life. Change the oil every 25 operating hours to reduce undue engine wear. Clean the air filter at the same time (more often if the machine operates in dusty conditions). Refer to your owner’s manual for detailed instructions, and see Caring for Power Equipment.

Be sure your mower blade is sharp. A sharp blade will make a nicer cut, reduce grass clippings and won’t damage grass blades.