How to Tune Up a Lawn Mower Video


An annual tune-up extends your lawn mower's life and improves its performance.

If your mower has bigger problems than a tune-up can fix, see our lawn mower repair help for troubleshooting advice and step-by-step mower repair instructions. 

How to tune up a walk-behind gas lawn mower


It’s best to tune up your mower’s engine once a year. Following your manual's service schedule will reduce the need for costly repairs later. The tune-up procedure shown here is for most mowers.

The parts you will need to do the tune-up are a spark plug, an air filter and one quart of four-cycle engine oil. You can order these parts at or by calling 1-800-252-1698.

Write down the exact model number for your lawn mower, including dashes, periods and other characters. You need this complete number to ensure you order the correct parts.

Equipment and Tools You Need

  • Safety glasses
  • Work gloves
  • Spark plug gap tool
  • Screwdriver to remove the air filter
  • Putty knife
  • Oil funnel
  • Approved oil drain pan
  • Plastic bag
  • Clean rags or paper towels
  • Lubricant such as WD-40

Before You Begin

In a well-ventilated area, start the mower and let it run for about five minutes. This will expend any metal particles that have settled in the bottom of the engine. It also warms the oil so that it will drain faster.

Change the Oil and Clean Under the Deck

After the engine is warm, stop the engine. With a gloved hand remove the spark plug wire; be careful as the engine is hot. To prevent gas from leaking when you turn the mower on its side, cover the gas tank with a plastic bag secured by the gas cap. Next remove the dipstick from the engine and wipe the oil off the dipstick with a paper towel or shop rag. Then place the dipstick in a safe place.

Now, position the approved oil container next to the mower. Then tip the mower so the dipstick tube is toward the ground. Be sure that the oil is draining into the drain pan while you are tipping the mower.

While you're waiting for the oil to drain, it's a good time to clean the underside of the mower housing. Remove the blade to prevent injury. You can use a putty knife to remove any grass buildup. While you're looking under the deck, inspect the condition of the blade. If the blade is dull, nicked or bent, replace it.

Hold the blade against the blade adapter with one hand and thread the blade bolt with the other. Holding the blade with one hand, tighten the bolt with a torque wrench. The blade should be tightened between 450 inch-pounds minimum and 600 inch-pounds maximum.

After the oil is drained, tip the mower back over. Pour the oil into a sealed container and dispose of it in accordance with applicable law. Most Sears Automotive stores accept used oil for recycling. Call your local Sears Auto Center for details.  Be sure to wipe up any oil that may have spilled in the process.

Now you need to refill the engine with oil. Using a funnel, carefully pour the oil into the dipstick tube. Only pour in about three quarters of the amount recommended in the owner’s manual. Check the oil level with the oil level dipstick and add as needed to reach the target level. Replace the dipstick and screw it on tight.

Change the Spark Plug

Now it’s time to replace the spark plug. Use the spark plug wrench to remove the spark plug. The engine may still be warm. Before installing the new spark plug, set the spark plug gap to .030. Thread the new spark plug in by hand. Then tighten it with a spark plug wrench.

Replace the Air Filter

Next replace the air filter. Remove the air filter cover with the correct size screwdriver. Once the cover is removed, discard the old filter. Before installing the new filter, use a clean rag or paper towel to wipe any debris out of the cover and around the air filter body. Once it’s clean, install the new filter. Put the cover back on and replace the screws.


Lubricate the pivot points for the engine control. Use a lubricating spray such as WD-40 on each side and work the lever up and down to ensure it moves freely. If you placed a bag under the gas cap, unscrew the cap and remove the bag. The last step is to reconnect the spark plug wire.

Tuning up your mower once a year helps you get the best performance and extend the life of your mower. For troubleshooting tips, step-by-step repair guides and more articles and videos, check out our lawn mower repair help section.