Where Is The Spark Plug On A Lawn Mower? And How To Replace It

If you’re like most people, you’ve never pulled out and replaced the spark plug on your lawn mower.

So today, we will run through where to find the spark plug – whether you have a riding mower or walk-behind mower – and how to replace it.

First you’ll see a quick guide with video to get started right away.

And after, we’ll go into more detail about spark plugs.

Let’s jump in.

Quick Guide – Spark Plug Replacement

Walk-behind Mower

  • The spark plug on a walk-behind mower engine will be at the front or top.
  • You can easily spot it because it has the spark plug wire attached to it. The plug wire will be the only visible wire/cable on the front of the engine so you know the spark plug is underneath it.
  • Remove the plug wire by pulling it.
  • Now with the spark plug visible you can use a socket wrench or spark plug wrench tool to twist and remove it.
  • Put new spark plug on the engine the opposite of how you took the old one off. Tighten it snug.
  • Re-attach the spark plug wire.

Watch this video from Briggs & Stratton on how to replace a spark plug:

Riding Mower

  • A riding mower may have more than one spark plugs. Check your manual to know.
  • Depending on your type of riding mower your engine will be under either the seat, behind the seat or with a lawn tractor in front under a hood.
  • Lift up part of mower protecting the engine and look for the spark plug wires. You will know they are the spark plug wire because they have an elbow at the connection point. Also, with a slight pull they will easily come off. So if you tug on the wrong wire it will not budge.
  • Use a socket wrench or spark plug wrench tool to remove the spark plug.
  • Install new one in its place with the same tools.
  • Put wire back onto end.
  • Start mower to make sure everything is working.

Watch this video demonstrating spark plug replacement on a riding mower:

Where Is The Spark Plug On A Lawn Mower & What Does It Do?

Oftentimes, we will notice that our lawn mower isn’t working as efficiently as it used to and chalk it up to the blades being dull. However, it may be something as simple as a dirty or fouled spark plug.

The lawn mower spark plug is located on the side of the engine. It is usually covered by a metal or plastic cover. The spark plug ignites the mixture of air and fuel in the engine, which powers the lawn mower.

Spark plug location on Honda small engine

The spark plug has two main functions:

  • To provide a spark that ignites the fuel-air mixture
  • To help prevent engine “knocks” or “pinging” by creating an explosion that is timed correctly

If the spark plug becomes fouled with deposits, it will not be able to create a strong enough spark to ignite the fuel-air mixture. This can cause the lawn mower’s engine to run poorly or not at all. Cleaning or replacing the spark plug will usually fix this problem.

How Do You Know If The Spark Plug Needs To Be Replaced?

One of the most important parts of your lawn mower is the spark plug. This small component helps to create the spark that ignites the fuel, powering the engine.

Over time, however, spark plugs can become fouled by deposits of oil and carbon. When this happens, they can no longer create a strong enough spark to start the engine. As a result, it’s important to regularly check your spark plug and replace it if necessary.

Spark plug failure modes

There are a few easy ways to tell if your plug needs to be replaced:

  • Check out the image above of different failed spark plugs and why they failed.
  • If your spark plug looks like one of them you know why it failed.
  • Check the condition of the metal tip. If it is dry and corroded, then it’s time for a new plug.
  • Pull on the spark plug lead. If it comes off easily, then the connection is loose and needs to be tightened.
  • Finally, try starting the engine. If it takes several attempts or fails to start altogether, then the problem is likely with the spark plug.

By following these simple tips, you can keep your lawn mower running smoothly all season long.

How To Replace The Spark Plug On A Lawn Mower Yourself

Changing spark plugs on a lawn mower is a relatively simple task that can be completed with a few tools that are likely already in your toolbox.

The most important tool you’ll need is a ratchet and socket set. You’ll also need a spark plug wrench, which is a specialized tool that’s designed to remove and install spark plugs without damaging them.

If you don’t have one of these wrenches, a pair of pliers will work in a pinch. Finally, you’ll need a can of starting fluid. This isn’t strictly necessary, but it will make starting the lawn mower easier if the engine is cold.

  • To replace the spark plug, first, remove the air filter cover. This will give you access to the spark plug boot, which is attached to the end of the spark plug wire.
  • Using your ratchet and socket set, remove the nut that secures the boot to the spark plug socket.
  • Once the boot is removed, you can use your spark plug wrench (or pliers) to remove the old spark plug from the engine. Don’t worry if it’s a little tricky to get out – just apply some pressure and it should eventually come loose.
  • Once the old plug is out, screw in the new spark plug by hand. Once the spark plug gauge is tight, use your ratchet to give it an extra quarter turn. This will ensure that the spark plug is properly seated.
  • Finally, reattach the spark plug boot and air filter cover, then try starting the lawn mower. If it doesn’t start right away, squirt a little starting fluid into the carburetor and try again. With any luck, your lawn mower will be up and running in no time!

Things To Do Regularly To Maintain The Spark Plug

Most people know that they need to regularly change the spark plugs on their lawn mower, but there are a few other things that you can do to keep them in good working condition.

  • First, make sure that the spark plug gap is set correctly. This can be done with a feeler gauge or by consulting your owner’s manual.
  • Next, clean the spark plug regularly with a wire brush.
  • Finally, replace the spark plug if it shows signs of wear or damage.

By following these simple steps, you can ensure that your lawn mower’s spark plugs will always be in good working condition.

Do You Need A Specific Type/Brand/Model Of Spark Plug In Your Mower?

There’s a lot to consider when purchasing spark plugs for your lawn mower.

Depending on the make and model of your mower, you may need a specific type or brand of the spark plug.

In general, however, you can use any type of spark plug as long as it fits the requirements of your mower. Be sure to check the owner’s manual for your mower to ensure that you’re using the correct type of spark plug.

You should also keep an eye on the condition of the spark plug. If it starts to wear out, it will need to be replaced. Otherwise, you risk damaging your mower or causing it to malfunction. Regular spark plug maintenance is essential to keeping your lawn mower running smooth, so be sure to keep an eye on all of its parts – including the spark plugs.

Wrapping Up:

As you can see, the spark plug is located on the side or top of the lawn mower. It is a small, cylinder shaped object that screws into the side of the engine. The spark plug helps to create the spark that ignites the fuel in the engine, which starts the lawn mower.

If you’re having trouble finding or replacing the spark plug on your lawn mower, be sure to consult your owner’s manual.

Further Reading

  1. As part of regular lawn mower maintenance be sure you also know how to change the oil.
  2. For the best results from your lawn mower for years to come be sure to only buy one of the best mowers. Check out our guide of the 7 best.
  3. How big is your lawn and how long will it take to mow? Here is how long it takes to mow 1 acre depending on the type of mower you’re using.

About your guide: Jamey Kramar is a certified Lawn Care Manager and a Mechanical Engineer by trade. He has been writing about outdoor power equipment for 11 years and has been quoted in NYTimes, Popular Mechanics, HowStuffWorks, iFixit, Realtor.com, and more. He spends his spare time disassembling things and also building an off-grid cabin at his 200-acre property.