Tune Up a Lawn Mower

• Step 1 Be safe

  Start by reading all safety information in your lawn mower's manual, especially about handling the blade and disconnecting the spark plug wire.

  Wear heavy leather gloves and protective eyewear as you work.

  Remove the spark plug wire. This important step prevents the lawn mower from starting accidentally during the tune-up.

• Step 2 Drain old gasoline

  You should burn off or drain gas from your lawn mower at the end of the mowing season, but if you skipped it last fall, use a turkey baster to suck old fuel from the tank. You don't have to drain your gas if you added fuel stabilizer within the last six months.

  Deposit the gas in a container approved for gas storage and dispose of it according to local regulations.

• Step 3 Sharpen or replace the blade

  

  Carefully tilt the lawn mower on its side with the fuel tank's fill hole facing up. Grasp the blade with a gloved hand to keep it from turning when you remove the blade bolt. Remove the bolt and washer, put them where you're sure to find them later and remove the blade.

  Inspect the blade and decide whether to sharpen it or replace it, following these guidelines:

  • If the blade is deeply chipped or cracked, replace it with a new blade.
  • If the blade is dull or has small chips, take your lawn mower to a local hardware store or service center to have it sharpened.
  • Sharpen the blade yourself if you have the know-how and tools.

  When reattaching the blade, follow the blade's torque specifications, which usually range from 35 to 40 ft. lbs. Use a torque wrench to achieve the proper spec for your lawn mower.
  

• Step 4 Scrape the underside

  With the lawn mower still tilted onto its side, use a metal scraper or screwdriver to scrape off dirt and grass that have caked onto the underside.

• Step 5 Change the spark plug

  

  Use a socket wrench to carefully remove your lawn mower's old spark plug. If there's debris around the spark plug hole, scrape it away with a small wire brush, taking care not to let any fall into the opening.

  If the new spark plug isn't pre-gapped, gap the space between the sparking pin and the bracket with a spark plug gap guage.

  Screw in and tighten the new spark plug by hand. Use the socket wrench to give the plug a quarter turn.

• Step 6 Replace the air filter

  If your lawn mower has an air filter, you might need to replace it, particularly if you live in a dusty area.

  • If it's a cylinder, unscrew it and remove the filter.
  • If it's a box, you might need to use a screwdriver to dislodge the cover.

  Tap the filter on a hard surface to shake out dirt. If the filter is plugged or especially dirty, replace it with a new filter.

• Step 7 Add gas and change the oil

  

  Fill the lawn mower's fuel tank with fresh gasoline.

  Reattach the spark plug wire and then run the mower for a few minutes to warm the oil so it flows faster.

  Turn the lawn mower off and detach the spark plug wire. Carefully tilt the lawn mower with the spark plug facing up.

  Place an approved oil collection pan under the dipstick and remove the dipstick. Drain the oil from the mower into the pan and then refill the tank with fresh oil of the type specified in your owner's manual.

  Return the lawn mower to its upright position and reconnect the spark plug. Dispose of the oil according to local regulations.

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