May 31, 2019

How to tune up a lawn mower video

How to tune up a walk-behind lawn mower.
How to tune up a walk-behind lawn mower.

You can help the engine on your walk-behind lawn mower run better and last longer by giving it a tune-up at least once a year. A tune-up takes about half an hour and involves changing the oil, air filter and spark plug, along with cleaning the exhaust, controls and engine cooling system. This video walks you through the process so you can keep your engine performing its best.

For additional repair help, including common symptoms and troubleshooting tips, step-by-step lawn mower repair guides and articles, check out our repair help section. In addition, find the lawn mower parts you need to fix your mower.

Hi, Wayne here from Sears PartsDirect. Did you know that tuning up the engine on your lawn mower at least once a year helps it last longer and perform better? It doesn’t take that long either—we’ll show you how in this video.

Supplies you may need

  • Oil

  • Drain pan

  • Air filter

  • Spark plug

  • Spark plug wrench

  • Spark plug gap tool

  • Feeler gauge

  • Wrench or nut driver set

  • Plastic bag

  • Shop rags

  • Cleaning brush

  • Work gloves

  • Safety goggles

  • Compressed air supply (optional)

When buying supplies, make sure to get the spark plug and air filter that fit your engine. You also need motor oil, a drain pan, a spark plug wrench, a wrench or nut driver set, shop rags, a cleaning brush, work gloves and safety goggles.

Before you begin

Look up the engine oil capacity in the engine owner's manual so you know how much to add when changing the oil.

In a well-ventilated area, check fuel level in the gas tank. The tank should be nearly empty before starting the tune-up so fuel doesn't spill when you tip the mower.

If the tank has fuel, run the mower to empty most of the fuel or drain most of it out of the tank.

Just before beginning the oil change, run the engine for 5 minutes to warm the oil so it drains faster. If you ran the engine to empty the fuel tank, let the engine cool for about 20 minutes. The oil will still be warm enough.

Put the mower on a level surface.

Wearing safety goggles and work gloves, remove the fuel tank cap. Place a plastic bag over the fuel tank opening and put the fuel tank cap back on to prevent gasoline from leaking out through the fuel tank cap vent.

Remove the spark plug wire; be careful because the engine is hot.

Change the oil

Remove the dipstick and wipe it clean with a shop rag.

Put the drain pan next to the mower.

Tip the mower to drain the oil from the dipstick tube and into the drain pan.

After the oil drains, set the mower upright and wipe up any spilled oil.

Carefully pour new oil into the dipstick tube. Start by pouring in three quarters of the amount of your engine’s oil capacity, because some oil might be left in the mower.

Wait a minute for the oil to settle in the engine sump.

To check the oil level, push the dipstick all the way into the dipstick opening and lock it.

Then unlock and pull out the dipstick. If the oil doesn’t reach the top of the full mark on the dipstick, add a little more oil, wait a minute and check again.

Repeat until oil reaches the top of the full mark. Reinsert the dipstick.

Take off the fuel tank cap, remove the plastic bag and reinstall the cap.

Replace the air filter and change the spark plug

Next, we'll change the air filter. Release the locking tab and pull off the air filter cover. Remove the old air filter and install the new filter. Reinstall the air filter cover.

To replace the spark plug, use a spark plug wrench to remove the old plug from the engine cylinder. Using a gap tool and feeler gauge, set the gap on the new spark plug to the specifications in your engine owner’s manual. For this engine, the gap is 0.02 inches. Thread the new spark plug into the engine and tighten it with the wrench. Don’t reconnect the spark plug wire yet.

Clean the engine

The next step is to clean the engine when the engine and muffler are completely cool. Release the starter rope from the lawn mower handle. Remove the screws from the blower housing and pull the housing off the engine.

Clean the muffler and engine cooling fins using the cleaning brush and shop rags. Also clean the choke and throttle rods, springs and linkages. Use the brush to remove debris from the rewind starter grill.

You can also blow debris and dirt off the engine and controls using compressed air.

When you’re done, reinstall the blower housing and connect the spark plug wire.

Re-check the oil level

Now that we have everything installed, let’s start the engine and re-check the oil level. In a well-ventilated area, run the engine for a few minutes to move the oil through the engine. Then shut the mower off. Allow a minute for the oil to settle in the engine sump. Remove the dipstick and check oil level.

Add oil if needed to hit the full mark on the dipstick.

That’s it, the tune-up’s complete and you’re ready to start another season of mowing.

I hope this video helps you out today. You can find links to the parts and products we talked about in the video description below. Check out our other videos here on the Sears PartsDirect YouTube channel. Subscribe, and we’ll let you know when we post new videos.

Symptoms for gas walk-behind mowers

Choose a symptom to see related walk-behind mower repairs.

Main causes: uneven wheel height settings, damaged wheel, dull or damaged cutting blade
Main causes: damaged cutting blade, loose cutting blade, damaged flywheel key, engine needs tune up
Main causes: engine needs tune up, dirty or clogged carburetor, damaged flywheel key
Main causes: dirty carburetor, bad spark plug, clogged air filter, engine choke problems, clogged gas cap vent
Main causes: drive control cable failure, worn or broken drive belt, bad transmission, broken drive wheel
Main causes: stale gas, engine needs tune up, bad spark plug, dead battery, bad recoil starter, faulty safety switch, bad ignition coil

Repair guides for gas walk-behind mowers

These step-by-step repair guides will help you safely fix what’s broken on your walk-behind lawn mower.

How to replace a lawn mower spark plug

Take a few minutes to replace the spark plug during your lawn mower's annual tune-up or if the spark plug is burnt or cracked.

Repair difficulty
Time required
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How to replace a lawn mower blade

Check your lawn mower blade regularly and replaced it if it's bent or damaged.

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How to replace a lawn mower flywheel key on a flathead engine

When you hit a hard object with your mower, the flywheel can shear to protect more expensive components. Learn how to replace this tiny but essential part.

Repair difficulty
Time required
 45 minutes or less

Articles and videos for gas walk-behind mowers

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