Top 5 Best Spark Plugs For Harley Davidson (2020 Review)

Are you looking for the best spark plugs for a Harley Davidson?

You're in the right place!

In this guide, you will learn:

  • Which spark plugs are the best for your Harley Davidson
  • Tips on spark plug installation and inspection
  • How to tune your Harley to perfection

And much more!

Top 5 Best Spark Plugs For Harley Davidson (2020 Review)
Image Product


E3 Powersports Spark Plug
  • Yttrium-enhanced alloy
  • Designed for high performance
  • Used by professional drivers
  • Yttrium-enhanced alloy
  • Designed for high performance
  • Used by professional drivers
View on Amazon


NGK Iridium IX Spark Plugs
  • Pre-gapped
  • Enhanced anti-corrosion qualities
  • An industry leader in spark plug technology
  • Pre-gapped
  • Enhanced anti-corrosion qualities
  • An industry leader in spark plug technology
View on Amazon


Pulstar Spark Plugs
  • Plasma assisted combustion technology
  • Adds up to 7 HP
  • Improved throttle response and idling
  • Plasma assisted combustion technology
  • Adds up to 7 HP
  • Improved throttle response and idling
View on Amazon


Denso IXU22 Iridum Power Spark Plugs
  • 360-degree laser-welded technology
  • U-groove ground electrode
  • Maximizes firing potential
  • 360-degree laser-welded technology
  • U-groove ground electrode
  • Maximizes firing potential
View on Amazon


ACCEL 6R12 Spark Plugs
  • Improved throttle response and fuel economy
  • Sold in sets of two
  • Made especially for Harley Davidson
  • Improved throttle response and fuel economy
  • Sold in sets of two
  • Made especially for Harley Davidson
View on Amazon

Overall #1 Rated Pick

Updated As of 5/20/2020

Top Rated Overall:

E3 Powersports Spark Plug

  • Yttrium-enhanced alloy
  • Designed for high performance
  • Used by professional drivers

E3 spark plugs have made a productive modification to their spark plugs using a diamond-shaped tip they call the diamond fire design that is designed for smoother acceleration, more power, higher efficiency, and higher ecology by burning off carbon deposits emissions more completely.

Choose E3 because they are produced in the USA with your Harley Davidson's performance in mind.

Just be sure to verify that you are purchasing the right part by entering your Harley Davidson's year, make and model into the Amazon search platform.

You could also verify the right fit by entering your VIN into your local auto parts store's website.

Tuning up your Harley is one of those tasks that is soothing on the soul.

And if you are going to tune up your classic motorcycle there is no doubt you want quality parts. 

We want you to be aware of the best; check out our list of the best spark plugs for Harley Davidson below to learn a thing or two.

Looking for a pair/set of HD plugs? Here are some of the high-quality go-to aftermarket options for Harley Davidson spark plugs aside from the OEM spark plugs that you can purchase on the Harley Davidson website.

These are some of the coolest street motorcycles on the planet; Harley Davidson is a company that survived the great depression--how's that for resilient? It's time you showed your Harley a little love.

Read More >> What Are The Best Spark Plugs For a 4.3 Vortec Engine?

Top 5 Best Spark Plugs for a Harley Davidson

Check out our below list for a summary of our results. Keep on reading to learn more about your other options!

How To Change Spark Plugs For Your Harley Davidson?

Changing the spark plugs on a Harley is too easy, but to do it the proper way you'll need these tools:

  • Spark plug socket
  • Spark plug gap tool/feeler gauges
  • Torque wrench
  • Ratchet

Start by simply tugging the spark plug wire boot off each spark plug at the top of the cylinder head. 

From there, you should be able to fit a spark plug socket onto the spark plug and remove it from the cylinder head.

Inspect the spark plug for fouling.

Check the gap of the new spark plug to the manufacturer's specification. You can do this with feeler gauges or a spark plug gap tool.

When everything checks out, install the new spark plug, and torque it to the manufacturer's specification to avoid engine damage and guarantee the max performance.

Replace the spark plug wire boot and fire up that engine.

You now have new spark plugs; go and rip your Harley around the block and enjoy smooth firing engine performance.  

Read More >> What Does a Bad Spark Plug Look Like?

Are There Different Types of Spark Plugs For Harley Davidson?

You are going to have more fun tricking your Harley out with cold air intake for an even meaner noise and performance, but spark plugs are also crucial to the performance of your Harley. 

There are different designs of spark plugs that you can try inside your Harley's engine and observe the results.

Copper plugs are the cheapest and most conventional type of spark plug that has the shortest life. You should replace traditional spark plugs every 10-20 thousand miles.

Spark plugs with a platinum electrode are just underneath iridium in quality and are said to last almost as long as iridium plugs. 

Iridium spark plugs are said to be the longest-lasting spark plug made today with the potential to last up to 100 thousand+ miles in vehicles. You should replace your iridium spark plugs every 60 thousand miles in your Harley Davidson.

Just to clarify: generally, all spark plugs have a copper core because copper insulates and conducts electricity better than any other metal. Precious metals like iridium and platinum are used in small amounts on the tip of the plug to prolong their life. 

There are also non-resistor spark plugs that might be useable on older Harley models. Chances are, though, if you are driving a newer Harley that has a radio then the non-resistor plugs will interfere with it and other electronic devices.

Read More >> How Do You Clean A Spark Plug Yourself?

Did you know: It only took 20 years for Harley Davidson motorcycles to become the largest motorcycle manufacturer in the world!

How Much Should I Pay For My Harley Davidson Spark Plugs?

You will be paying anything from just a few dollars for each spark plug to $20+ depending on the situation. 

Some Harley Davidsons take four spark plugs (two for each cylinder), so don't be surprised if you end up paying 50$ on a set of spark plugs for your Harley. 

There is always the cheapest option that will do the job, but this is your Harley Davidson we're talking about! Don't mess around with cheap parts inside a quality engine.

Thread Lengths

When replacing your spark plugs, hold the old and new plugs side by side and inspect the length of the threaded part of the spark plug. They should be the same. 

If the new spark plugs you purchased have longer threads do not try to install them in your bike because you will run the risk of knocking them against the pistons. 

Heat Range

There are spark plugs that are designed for extreme hot and cold riding conditions. Each spark plug manufacturer will usually indicate somewhere in the part number the heat range of the spark plug. For example, with NGK plugs the lower number indicates a hotter type, and a higher number indicates a colder type.  

So if you ride in extremely hot or extremely cold climates, or if you run your Harley Davidson at high rpm's constantly then you should consider heat range when purchasing your next set of spark plugs for the best performance results.

Read More >> How Do You Remove a Broken Spark Plug?

How To Choose The Spark Plug Wires For Harley Davidson?

It's always best to go with the OEM spark plug wires on quality engines. When riding on a Harley Davidson, you are sitting on top of a masterpiece that has been thoughtfully designed part by part. Keep your Harley running like a boss by going to the Harley Davidson website when in need of Harley Davidson spark plug wires.

There are also plenty of options on Amazon of spark plug wires that will fit your Harley Davidson. All you have to do is search something like 'Harley Davidson spark plug wires', or you could even enter the year and model of your Harley Davidson into Amazon and it will narrow your search results down to the exact match. 

How Long Should My Spark Plugs Last In My Harley Davidson?

You should realistically change the spark plugs about every 15,000 miles on your Harley to take advantage of the maximum performance. 

Harley Davidson is possibly one of the most famous motorcycle brands in the whole world, and they are known for holding your value over the years.

It's all a matter of how bad you want to protect your investment, and keep your Harley running new for decades like they are known for doing. 

If you fouled the new spark plug on your Harley, chances are there is an underlying problem that needs to be solved before installing another new one.

Otherwise, you will end up replacing the spark plug twice when the same problem that fouled the previous spark plug fouls the new one also.

However, if you are installing spark plugs simply for preventative maintenance then it depends on what the spark plug is made out of. 

Copper plugs usually last around 20 thousand miles, whereas iridium and platinum plugs last anywhere from 60-100 thousand miles. 

Harley Davidson even makes a gold spark plug for their motorcycles, however, they don't specify how long the gold-palladium will last in mileage. You can find and purchase Harley Davidson OEM spark plugs on their official website.

Read More >> What Are The Best Spark Plugs For Fuel Economy?

My Reviews Of The Best Harley Davidson Spark Plugs

E3 spark plugs are made in the USA and designed specifically for performance.

These E3 plugs are designed with colder heat ranges to allow for higher performance and durability in extreme conditions.

These Powersports spark plugs are recommended by professional drivers, and you can pick them up in packs of one on Amazon.

 This is a great choice for performance spark plugs, and you can verify that it's the right part for your specific bike by entering its information on the Amazon app.


  • High-performance design
  • Contains Yttrium-enhanced alloy
  • Designed for colder heat ranges


  • Cheaper options available
  • May not be compatible with all Harley Davidsons
  • Not an OEM part

NGK makes world-class spark plugs, and you can find NGK Iridium plugs in sets of two on Amazon that are made especially for the Harley Davidson twin cam engine.

NGK is one of the most dominant spark plug producers on the market today.

They are even looking to change their production over to electric batteries because of the changes in the automobile industry. 

NGK is aware of what goes on inside your engine, so you can trust they will sell you a good part for your Harley.

Check out NGK Iridium IX DCPR7EIX spark plugs as a possible great option for your Harley.


  • A leader in spark plug production
  • Made especially for Harley Davidson engines
  • Anti-corrosion qualities


  • Not an OEM part
  • More expensive
  • Risk of manufacturing errors in precious-metal layering

Give Pulstar a try if you are looking for a higher-end spark plugs purchase.

These are some of the most expensive spark plugs you could buy for your Harley Davidson with plasma-assisted technology and 'wicked fast' throttle response.

Spend the extra cash for a set of quality spark plugs that were developed with the help of the US Department of Energy Laboratory. 

Installing these plugs is said to add up to 7 horsepower and 9 ft-lbs of torque to your Harley.


  • Plasma-assisted technology
  • Fast throttle response time
  • Made in the USA


  • Expensive
  • Engine enhancement could be unnoticeable
  • Other options may be more enticing

These Denso spark plugs that are offered at a slightly cheaper price boast the 'world's smallest center electrode at .4 mm that is designed to maximize firing potential.

Denso plugs also have a taper cut and U-groove ground electrode that provides a faster spark of flame growth and makes for less heat quenching.

Denso plugs have a low voltage requirement that makes for easy engine starting and reliable performance.


  • 360-degree laser welded
  • U-groove ground electrode
  • .4 mm iridiumcenter electrode


  • Cheaper price could mean lower quality
  • Iridium dust can be flammable
  • Potential manufacturing errors in precious-metal layering

These Accel spark plugs come in packs of two and are made especially for Harley Davidson motorcycles.

Accel plugs improve throttle response and fuel economy, and they also produce a larger spark so that you have more power at higher RPMs.

You can expect less fouling when installing these Accel plugs into your Harley's engine.


  • Sold in sets of two
  • Made especially for Harley Davidsons
  • High performance


  • On the expensive side
  • No iridium/platinum
  • Not an OEM part

Verify that these E3 spark plugs are the right fit for your Harley Davidson either by using the measurements listed or asking a professional, and give them a shot.

You won't be let down. You could also plug the VIN into the online parts retailer to get the exact results for your bike. 

Support a part that is made in the USA, and compliment your American street bike by installing a high-performance part into its engine.

Try out some E3 spark plugs in your Harley the next time you go to replace the plugs and see the performance enhancement for yourself.

Final Thoughts On Spark Plugs For Harley Davidson

There's nothing like a finely tuned Sportster or Softail to ride around on. Here are some other quick tips to help you along the way in your journey of tuning up a classic:

How To Inspect a Spark Plug

Inspecting a spark plug is easy enough to do, but if you have never done it before there are some things you should know about proper spark plug inspection.

Inspect the white ceramic insulator for cracks or damage; an insulator that is cracked can easily cause a misfire. 

Also, inspect the electrode tips on the spark plug. Each tip should be dry and clear of carbon buildup. If you notice that one plug looks significantly different from the other whether its tip is burned and blistered or it is caked in oil, then you should investigate the problem further.

Is It Necessary To Use Anti-Seize On The Spark Plug Threads Before Installing?

Using anti-seize is recommended in the Harley Davidson owner's manual. Just remember to use a torque wrench to avoid the mistake of easily over-torquing spark plugs that have anti-seize on the threads.

Can You Reuse A Fouled Spark Plug?

You can clean a fouled spark plug and reuse it if it fouls up on you while driving. 

Clean the spark plugs off with some brake cleaner and a rag, or even use sandpaper or a brush to clean off the electrode tips of the spark plug and install them back into the motor after gapping them correctly.

You don't always need to purchase new spark plugs although some professionals will tell you to replace them always.

Read More >> What Are The Best Spark Plugs For a 5.3 Silverado?

How To Effectively Monitor Harley Performance

There are diagnostic modules that you can permanently install to the diagnostic port of Harley Davidsons for live performance monitoring through a smartphone app. After replacing your spark plugs, you will easily be able check to see if the engine has better engine stats, or if you fixed the misfiring plug effectively.

Monitoring your Harley Davidson through a tuner application is a beautiful thing. 

Is Your Harley Carbureted Or Fuel Injected?

Deciding which Harley Davidson to purchase has to be one of the easier chores in life. 

Do you know how your Harley Davidson gets its fuel? Chances are, if you are purchasing a model from the past 20 years then your Harley has direct fuel injection. 

Carburetor Jetting Is Key

If you are a fan of the retro Harley Davidson motorcycles, then you are going to want a carburetor that is jetted impeccably to ensure the best fuel economy and spark plug life. 

Your Harley Davidson motorcycle is an investment. Take care of it by performing the recommended maintenance when it needs to happen. 

Solving Ignition System Issues

When your engine starts to misfire it is very unnerving and not a lot of fun. The good news is that it doesn't have to be so complicated. 

You can solve ignition system issues by performing a few tests. 

  • Ignition coils

The first place to start when diagnosing an ignition problem is inspecting the spark plugs and the ignition coils. 

If the spark plugs seem to be in good condition, then you may want to try removing the ignition coils, trading them with each other, and reinstalling. You will know you have a bad ignition coil if the misfire is now in the opposing cylinder. 

  • Air filter

Remove the air filter and verify that it is not clogged with junk like sand and leaves.

  • Run a diagnostic check

Pulling the codes on your Harley will tell you what's up. Sometimes parts like crank position sensors go bad and cause a whole lot of engine problems.

  • Cylinder compression test

A cylinder compression test is one of the last tests that will help you diagnose your engine misfire. This requires a compression tester that screws into the cylinder head where the spark plug normally would.

After installing the compression tester, pull the fuse for the fuel injectors to eliminate fuel from being introduced into the combustion chamber. Then you can press the ignition on your Harley as if you were going to start it up. 

The gauge on the cylinder compression tester will show you how many PSI your Harley Davidson engine is currently producing. A normal number would be anywhere from 100-120 psi.

If you have a cylinder that tests at 90 psi or less, then this is most probably the cause of your misfire. It also means you have a bad valve seal/blown valve or piston rings that have failed. 

A failed compression test means that you'll have to rebuild the engine or cylinder head. Have fun!

Want More Power?

It's natural to want your Harley Davidson to go faster than ever. 

So what are some modifications you can make for the ideal Harley Davidson? 

  • Exhaust headers

You could try swapping out the headers for an upgraded set to liberate some horsepower

  • Cold Air Intake

cold air intake is one of the more common Harley Davidson modifications that consists of switching out the stock air intake to a conical cold air intake.

Adding a cool air intake is one of the most satisfying mods on your Harley. Not only will your Harley pull harder with a cold air intake, but it will sound even meaner.

Now You Know; It's Time For Results

You are now more informed on how to tune your Harley Davidson or any other motorcycle.

Keep us busy with any other questions you have concerning your Harley Davidson motorcycle. Here at ProperMechanic, we are your source for all things related to maintenance on any engine or vehicle.

Enjoy your classic American street bike!

About Your Mechanic

About Ryan Nichols

Ryan here! My pro mechanic career began as a technician for Mercedes-Benz. After two years of that great experience, I went out on my own in both the automotive and construction fields. I've since pulled my share of salvage yard parts and fixed more vehicles than I can count.

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