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How to Change a Lawn Mower Spark Plug Step-by-Step (With Pictures 2023)

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how to change lawn mower spark plugFrustrated from futile fighting with faulty, fragile four-stroke friends? Fret not, fellow frustrated four-stroke fan! Fresh spark, snappy start, steady sputter – follow my foolproof fix for frustration-free four-stroke fun.

Master maintenance and maximize mower might with my meticulous, mechanical methods. Liberate lackluster lawn-lovers longing to unleash their full power and potential.

I’ll illuminate installation, share specialty tools, and top tips for spark plug supremacy. You’ll be empowered to effortlessly excise and exchange exhausted plugs, taking total control of your mower’s power and performance.

Key Takeaways

  • Inspect spark plugs every 25 hours and replace if necessary.
  • Order replacement parts and schedule service online 24/7 through the dealer portal.
  • Use the proper tools and techniques to remove and inspect the old spark plug.
  • Follow the manufacturer’s instructions for installing the new spark plug and maintaining performance.

Tools and Materials Required

Tools and Materials Required
You’ll need some motor oil and a spark plug gapper to get ‘er done. Before yanking that ol’ plug out, make sure you’ve got the right socket size and a few rags handy.

That spark plug hole will be coated in grime, so soak up any oil that drips out when removing the plug. Inspect the electrode and toss that puppy if it’s blackened or corroded. It ain’t worth risking your safety starting a fire in the engine.

If she’s just got some deposits, scrape ’em off gently with a knife. Don’t sandblast the thing. Drop a bit of fresh oil down the plug hole and into the piston before screwing in the new plug by hand till snug.

Double-check your gapper for the right space between electrodes. There ain’t no room for sparks to jump on a tight gap.

Reconnect your wire and you’re set to mow.

Step-by-step Guide to Changing the Spark Plug

Step-by-step Guide to Changing the Spark Plug
Let’s begin by removing that old spark plug. First, locate and disconnect the spark plug wire, then use a wrench or socket to carefully unthread the plug. Next, inspect its condition to see if it simply needs cleaning or must be replaced entirely.

Don’t forget to lubricate the piston with a drop of oil before installing a new properly gapped plug by hand until it is just snug.

Locate and Disconnect the Spark Plug Wire

Disconnect that wire now so you can get in there and twist out the plug. Use the pliers to remove the spring clip holding the wire to the plug. Pull it straight off to disconnect it. Now your plug is free to be unthreaded. Be gentle when prying that wire off to avoid damaging the boot.

Remove the Spark Plug

Next, twist the plug counterclockwise slowly to remove it from the engine cylinder. Turn it several full rotations by hand until it pops loose. Be careful not to drop it into the cylinder. Inspect the electrode; light gray is okay, but black means a replacement is needed.

Use a wire brush to clean deposits if present. Apply a drop of oil in the hole to lubricate the piston before installing the new plug.

Determine if the Spark Plug Needs Cleaning or Replacement

Remove that cruddy plug and behold the electrodes, my friend. ‘Tis better to swap it than scrape, lest your mower fail to start come spring.

  1. Inspect for discoloration or corrosion.
  2. Check for carbon deposits or worn electrodes.
  3. If fouled, replace that sucker pronto.
  4. Ain’t no cleaning a dead spark plug, my man.

Swap in a new plug at the first sign of trouble. Your mower will thank you when it roars to life like a lion come spring.

Lubricate the Mower Piston

Protect her who brings life by gently drizzling your healing nectar before the metal screams again. Dip your fingers in the elixir, then let a single drop fall into the chamber to ease the turning of pistons.

This lubricates and prevents damage when the plug is rethreaded. New plugs can otherwise bind if installed dry, so this extra care extends engine life.

Inspect the New Spark Plug

While examining the new spark plug, check its gap against the engine manual’s specification, typically 0.

  • Scrutinize the electrode end for any defects or damage that could cause misfires.
  • Use a feeler gauge to accurately measure the gap between the center and side electrodes.
  • Compare the new plug’s gap to the old one to ensure proper replacement.
  • Adjust the gap by bending the ground electrode if needed, but don’t force it.

Carefully inspecting the new spark plug before installation prevents problems down the road when mowing.

How Long Does a Lawn Mower Spark Plug Last?

How Long Does a Lawn Mower Spark Plug Last
Sometimes your mower’s spark plugs can last up to two seasons of heavy mowing before needing replacement. For example, my neighbor Dave cuts his acre lot weekly and doesn’t replace his plugs for at least 100 hours of runtime.

Check spark plugs every 25 hours for signs of wear.

Replace sooner if the engine won’t start or lacks power.

Consider non-traditional ignition like magnetos for reduced maintenance.

Storing your mower properly overnight and out of season helps spark plugs last longer. But eventually, buildup and wear will impact performance, signaling the need for new plugs. Regular replacement ensures your mower starts easily and runs smoothly all season long.

Where to Find Lawn Mower Parts and Service

Where to Find Lawn Mower Parts and Service
You’ll find mower parts ‘n service through the dealer’s online portal. Just use Koenig MyDealer to order parts, schedule service appointments, and chat with certified technicians. This handy app lets you manage everything for all your outdoor power equipment from your phone or computer.

Action Method Benefit
Order Parts Browse thousands of parts diagrams to find exactly what you need. Add to cart and checkout online 24/7. Genuine OEM factory parts shipped to your door.
Schedule Service Book a service appointment online with our certified mechanics. Select day and time convenient for you. Experts diagnose issues and perform repairs and maintenance.
Access Resources Download manuals, safety guides, and DIY videos for self-service repairs. Detailed instructions to help you fix and maintain your equipment.

With Koenig MyDealer, you’ve got everything you need to repair, maintain, and operate your mower or tractor right at your fingertips.

Proper Installation of New Lawn Mower Spark Plugs

Proper Installation of New Lawn Mower Spark Plugs
When threading in the new plug, don’t get buck fever or you’ll strip the threads.

Inspect the old plug’s electrode for wear and corrosion. Light gray is ok, black means replace.

Check that the new plug’s gap matches the mower’s manual, usually 0.020-0.030 inches.

Apply a thin coat of oil to the plug’s threads to help ensure easy removal next time.

Gently snug the new spark plug by hand, then connect the wire. With care and the right tools, you’ll have that mower purring again in no time.

What is the Correct Spark Plug for My Lawnmower?

What is the Correct Spark Plug for My Lawnmower
Check your mower’s manual for its specifications to find the right spark plug model. Use the spark plug cross-reference chart below to match your engine’s requirements.

The material, heat range, and gap are key factors in choosing the proper plug. An incorrect or worn plug can cause hard starting, poor performance, or damage to the engine. When installing the new plug, apply a small amount of anti-seize compound to the threads to prevent seizing.

Be sure to gap the plug to the specified measurement for optimal ignition. With the right plug installed properly, your mower will start easily and run smoothly all season long.

Spark Plug Engine Type Gap
NGK BPR6ES Overhead valve, aluminum head 0.028-0.031 in
Champion RC12YC Flathead, cast iron sleeve 0.030 in
Bosch WSR6F Overhead cam, electronic ignition 0.035 in
E3 E3.36 Compact engines under 300cc 0.025-0.030 in

Frequently Asked Questions (FAQs)

How do I know when it’s time to change my lawn mower’s spark plug?

Engine hard to start or runs rough, lack of power, increased fuel consumption, excessive smoke from the exhaust. When in doubt, replace the plug – it’s an easy DIY job that will keep your mower running strong.

What safety precautions should I take when changing a lawn mower spark plug?

Disconnect the wire before you remove the old plug. Make sure the mower isn’t running. Wear gloves and eye protection – a spark could jump, and metal may be hot. Check for fuel leaks once the new plug is installed.

Will changing my lawn mower’s spark plug improve its performance?

You bet it will! A fresh spark plug can really wake up a tired mower engine. You’ll get easier, more reliable starts and smoother performance once that new plug is firing properly. Just be sure the gap is set right before installing it. A correctly gapped plug will deliver maximum power.

What are some troubleshooting tips if my lawn mower won’t start after changing the spark plug?

My friend, spark plug changed yet mower won’t awaken? Fuel mix too rich could be choking the dream. Or wire kinked, fuel filter clogged, piston ring stuck; she yearns to spin free. With care we’ll find where flow’s dammed or connection missed; then this sleeping beauty you’ll easily kiss awake.

How can I find the right spark plug for my specific lawn mower make and model?

To find the right spark plug, check your mower’s manual or model number plate for the make and model. Then visit the dealer or manufacturer’s website and search for the recommended plugs in the parts list.


Alright, y’all. That covers the basics of how to change a lawn mower spark plug from start to finish. I know some of you think it’s too much of a hassle, but don’t be intimidated. With the right tools and a little know-how, you can swap out an old plug in no time.

This’ll keep your mower running smoothly all season long. And remember—if you ever get stuck, your local shop is always here to help get your machine back up and cutting.

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Mutasim Sweileh

Mutasim is a published author and software engineer and agriculture expert from the US. To date, he has helped thousands of people make their yards lush and thick.