What Spark Plug to Use for Lawn Mower? (Complete Guide)

(Last Updated On: September 10, 2022)

Do you ever feel, Lawn mowing is a tedious job? And if the engine of your lawn mowing machine keeps cutting off because of its outdated spark plug, it becomes more disturbing. In such a case, changing the spark plug should be the to-do thing. Now questions may arise regarding– What Spark Plug To Use For Lawn Mower?

Well, worry not because we have got you covered. This piece of writing will guide you – on how to choose the right spark plugs and will address a few other queries relating to choosing lawn mower spark plugs.

Identifying the Bad Spark Plugs – First Thing First You may be wondering how to know if it is time to replace the spark plug. When the plug of your engine goes bad, you will face different kinds of issues with running the machine.

Identifying- Symptoms of Bad Spark Plugs

Several causes or symptoms may appear when your spark plugs not working properly. And you can easily identify it. Let’s know about some mostly faced symptoms so that you know whether or not the problem is with your spark plugs.

1. Difficulty With Starting The Engines

This is the most commonly occurring problem when the spark plug is bad. The land mower gets harder than normal to start.

If it’s a push mower, then it will require more pulls than necessary, and if it’s a lawn tractor, then turning the key once won’t start the engine. This happens when the sparks created by the plug are too weak to ignite the fuel.

2. Engine Performing Poorly

Even after you have managed to start the engine, it will cut off after a while. You will have to crank the engine again, which will be more difficult now because of the heat produced.

The expansion caused by heat, in the gap between the plug’s center and firing electrodes, will weaken the ignition.

3. Excessive Fuel Consumption

On top of those, if your mower engine starts consuming fuel more than normal, then be sure of what to blame. Plug creating weak sparks messes up the fuel burn and increases the consumption. If you notice that the engine is out of fuel more frequently than necessary, your poor plug might be the culprit.

4. Error In The Physical Appearance

Detach your spark plug and perform a check to see if it has Flathead Engine Spark Plugs & Gaps. The center electrode of the plug should have its top flat. If you find that to be round, then you might need replacement it. Furthermore, any kind of damage to the body will require a replacement spark plug.

What Spark Plug to Use for Lawn Mower? (How to Choose)

Spark Plug Type Chart

This is easier than you think. But one thing you need to remember is that spark plugs for lawn mowers are different from those of automobiles. The key differences are that the size and length of the thread of sparks plugs are greater in an automobile than in a lawnmower. So, make sure you don’t confuse between the types.

Mower Small engine spark plugs used are differentiated by factors like engine model, sizes, heat range, and gap. You have to ensure and choose the right spark plug that fits your engine’s gap and make sure it is attached tightly.

Anyway, follow these easy steps to find out the perfect and right spark plugs.

1. Matching with Old Spark Plugs

Exactly! Disconnect the plug wire along with the rubber cap. Then use a wrench to twist and detach your old plug from the engine. You may write the part number. Then take the plug to the store and buy a new one matching that.

Pro Tips: with these easy tricks you can also check or change your other vehicle plugs too. Like, cars, trillers, pressure washers, etc.

2. Check Your Lawn Mower Manual Book

If you somehow do not have the old plug, no worries. You can also read the manual that came along with your lawnmower.

Instructions on what types of plugs you can use should be found there. If not, just learn about the model of the lawnmower or the engine. Take the details to the store; they will help you find them out for you.

3. Check It Yourself With Gap Checker

You can also take a new plug and check its gap, using a gap checker. For sure! Most of the spark plug’s gap is 0.030 inches (0.76 mm), while some are less or more, like 0.040 inches (1.02 mm).

You can also adjust the gap yourself using the gap opener in that checker. Find the one that matches your required gap, and you’re good to go.

How to Check Performance and Fix – Spark Plug Not Firing Issue

You might sometimes want to check the ignition spark of your plug to see if it’s going well. There are spark plug testers that you can use.

Disconnect the ignition coil, and connect the tester in between the coil and the plug. Now, rest it aside and crank your engine.

Check if your plug is sparking or not. If your plug is flashing with a small light, it is sparking. And if there is no fire at all, then your plug is not sparking. You can also check it by using a screwdriver on the ignition coil.

Checking spark fire in clear view. Let’s watch a video-How it looks like?

How Often to Change Lawn Mower Spark Plugs?

It depends on your usage to decide how often you should replace the mowers spark plug. It’s recommended to change once a year at least. Anyway, you can keep your plug for two straight years, if the rate of your usage is not so high. As long as it functions well, you can keep it.

Lawn Mower Spark Plug Gap Chart

Spark Plug Type and Lawn Mower Spark Plug Gap Chart

You know! 8 mm to 14 mm plugs sizes are available in the market. But 10 mm to 12 mm sizes are the most commonly used spark plugs. Even it can be over 14 mm+ for exceptional mower engines.

Anyway, to understand a clear mindset on mower plug sizes and gaps you may keep eye on this image below. It will help you more.

How to Clean a Spark Plugs?

After long use, you will locate dark soot over the plug made from carbon. It is better off to clean that up.

The recommended way of cleaning plugs is a wire brush to rub over them and use plug cleaner spray, which is specifically made for cleaning the ignition area.

However, keep in mind that you should never use shot blasters or abrasives to clean the plugs, ever!

Lawn Mowers Spark Plug lifespan Time– How Long it Goes?

A regular lawn mower sparks plug can serve you up to two years, though it depends on usage. You should clean the plug regularly to have it last longer.

Sometimes the engine may not work properly because of the oil-smeared over the plug. In this case, you don’t have to switch the plugs at all. Just clean it and reattach it, your engine will work fine!

How to tell if a lawn mower spark plug is bad?

There are a few ways to tell if a spark plug is bad. One way is to look at the end of the spark plug. If the end is black or damaged, it may be time to replace the plug.

Another way to tell if a spark plug is bad is by looking at the color of the wire attached to it. If the wire is white, it means that there is no longer a good connection between the electrode and ground, and this can cause misfires.

Finally, you can try starting your lawn mower with a new spark plugs in place of your old one’s just to see how they perform side-by-side!

Final Words

Now you know how easily you perform maintenance on your lawnmower if the problem comes from the spark plug. Also, now you have a clear idea of how long maintenance time should need to change the spark plug at home or garage.

That’s all about lawn mower spark plug choosing and replacing guides. Hope you’ll enjoy our complete guides.

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Mitchel Shawn was a Co-worker and Engineer of a Gardening Tool manufacturing company since 2013 and a passionate researcher on Machinery goods. Picking the right tools for your work-station and making life easier is an untold helping journey by SHAWN. With this Reviewer Guides Blog, you'll definitely get help in revealing the accurate product spec which actually helps in real life works.