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The Complete Guide For Cleaning Your Spark Plug

Spark plugs are in every gas powered small engine and many DIY tune-ups will require you to clean them. From regular maintenance for efficient operation to fixing damaged machines, knowing how to clean a spark plug will help your motored machines run smoothly.

1. Pop Out The Spark Plug

If the spark plug is protected by a shroud or cover, remove it. Then pull off the thick wire located on the top of the spark plug. The wire might not come off immediately; wiggle it back-and-forth to loosen it and keep pulling.

spark plug in a lawn mower

You can now use a spark plug wrench to unscrew the plug and pull it out of its socket.

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2. Check For Build-Up On The Spark Plug

Check the tip of the spark plug, the part that sits inside the engine’s combustion chamber. If the tip is dry and a light gray color, your engine is running well. If the tip has fluffy black carbon deposits, the engine needs more oil. If the tip is slick and oily, the engine needs less oil or might be burning extra crankcase oil.

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3. Wipe Down The Spark Plug

Buy some brake cleaner from an auto parts dealer. It usually comes in spray cans. If you cannot find any, WD-40 also works well for cleaning spark plugs.

Spray the cleaning solution on the plug, aiming for grimy spots. The cleaner will break down any dirt and gunk. With a clean rag, wipe off extra debris and repeat this process until the spark plug is clean as a whistle.

4. Thoroughly Clean The Spark Plug Tip

The tip is the most important part of a spark plug, because that is where the spark is generated, and therefore needs the most thorough cleaning. On the end of the spark plug that inserts into the engine, there is a small piece of metal: the electrode. When this gets dirty, it needs cleaning for the spark plug to perform properly.

There are several methods for cleaning the spark plug. You can use each on their own or combine them for the best results.

Using Sandpaper

spark plug cleaning with sand paper

You will need a piece of 220-grit sandpaper. Slip the sandpaper under the bent part of the electrode and start sanding. You want to remove discolored build-up on the metal. Run the sandpaper back and forth until you can see bare metal on the tip.

Using A File

File down any dirty parts of the spark plug. You can fit the file in between the spark plug and the electrode to clean every nook and cranny. File away any build-up until you can see clean metal beneath.

Using A Wire Brush

spark plug cleaning with a wire brush

Take a wire brush and scrub at the threads of the spark plug. This will clean off oil and dirt, which makes it easier to put it back into the engine. Scrub in the same direction as the threads to clean most of the dirt off, then switch angles to finish off the cleaning job.

You do not need perfectly dirt-free threads, but get the biggest clumps cleaned up. I recommend wearing gloves while doing this cleaning to avoid stabbing your hands with the wire brush.

Using A Blowtorch

First off, safety. Wear gloves to protect your hands from the flames and hot metal. Additionally, hold the spark plug with a pair of pliers so you do not handle the hot plug directly. Use long pliers to hold it as far away from yourself as possible. Try not to clamp down too hard with the pliers so that you do not damage the spark plug, but still get a secure grip.

Turn on the blowtorch and hold the spark plug inside the flame. Spark plugs are made to withstand high temperatures, such as when they are inside a running engine. The fire will ignite any leftover oil or fuel build-up on the plug and burn it off. Turn the plug around to get it evenly exposed to the flame.

Once you see the electrode start to glow red hot, remove the spark plug from the flame and shut off the blowtorch. Let the spark plug cool on a non-flammable surface.

5. Blow Off Debris With An Air Gun (Optional)

spark plug cleaning with air compressor

After you finish cleaning the spark plug, you can hit it with pressurized air to blow off any remaining loose dirt or dust. You will need to slip the tip of your air gun into the spark plug’s hole, so attach an appropriate tip size. Use a long tip that can get as close as possible to the bottom of the spark plug’s well. Give it a few pumps to dislodge any debris and blow it all out.

6. Reinsert The Spark Plug

Before popping the spark plug back into the engine, you will need to set the gap between the plug and the electrode. There are gap tools you can use for this. Refer to the manual for your machine to find the exact measurement you need to set the gap to.

This video shows how to set the gap.

Then you simply need to screw the spark plug back into its socket using a spark plug wrench.

Next Steps

Congrats, you just cleaned a spark plug! When your machine refuses to start or seems to be running inefficiently, check out the spark plugs and see if they need cleaning. You should also check your plugs regularly to see if they are collecting engine build-up, perhaps every time you change your engine oil.

Frequently Asked Questions

How frequently should the spark plug on a small motor be changed?

If you take good care of your spark plug, it can last for years. I haven’t changed the spark plug in my lawn mower for several years now—however, I do clean it regularly as explained in this article.

Related: How Long Should Your Lawn Mower Last & How To Make It Last Longer?

A good rule of thumb would be to change the spark plug at the start of each mowing season or every 100 hours of use.

Does WD-40 work to clean spark plugs?

With time, particulate like dust and dirt will pile up around your spark plug. This should be cleaned off to improve performance, and WD-40 is a great way to do so.

The WD is short for Water Displacement, which means it pushes the water out of the way. If your spark plug is wet or if there is liquid around the igniter, WD-40 can be used as part of your cleaning routine to remove moisture. It also removes built-up carbon residue from the electrode.

Using WD-40 regularly can prevent moisture from corroding the mechanical parts of the motor, including the spark plug. It will also chew through corroded or rusted metal, which is useful if your spark plug is stuck and difficult to take in and out.