Best Spark Plugs for Harley Davidson in 2024 – Top 5 Picks

Best Spark Plugs for Harley Davidson in 2024 – Top 5 Picks

The best spark plugs for Harley Davidson are one of the most critical components that motorcycles’ engines depend on. They are responsible for initiating the combustion process. Since they provide consistent punches of electricity to start the engine, they wear and tear over time.

For this reason, it’s important to replace them regularly. But when your Harley Davidson’s spark plug fail, you don’t want to replace them with average units. Instead, you should get the best spark plug for Harley Davidson motorcycles.

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These plugs need to have premium materials to help them maintain optimal engine performance. Besides performance, high-quality spark plug for Harley Davidson can help to enhance the engine’s durability. Therefore, you won’t have to go through replacement processes often.

I’m a motorcycle enthusiast and have been in the industry for over a decade now. Therefore, I want to discuss what you need to look for when selecting the best spark plugs for Harley Davidson and also highlight the five best picks for 2022 and beyond.

Keep reading to find out more about these spark plug.

Top 5 Spark Plug for Harley Davidson

All Harley Davidson motorcycles require suitable spark plug for optimal engine performance. In the section below, we’ve compiled a list of top-quality spark plugs to help you find the perfect plug for your bike. The plugs on our list offer longevity, reliability, fuel efficiency, and unbeatable performance.

1. E3 Spark Plugs E3.36 Powersports Spark Plug – Best Sustainable Universal Fit

This E3.36 Premium Powersports spark plug is a high-performance spark plug offering smooth acceleration. It uses a gasket seat and has a reach plug designed for Powersports applications. Its thread reach measures 0.750 inches with a thread diameter of 12 mm and a gap size of 0.04 inches.

The plug features ground electrodes designed to reduce hydrocarbon emissions and fuel consumption. These ground electrodes secure to the housing using two legs. The legs facilitate heat dissipation and can withstand the intensity of engine vibrations for longer electrode life.

This E3.36 Premium Powersports spark plug is way more sustainable than all the Spark Plugs on our list. It provides more efficient fuel burning, thus creating more localized pressure in the cylinder.

Important Features

  • Reduces emission: It ensures a bright, clean spark for improved hydrocarbon emissions. The plug reduces emissions in both 2 or 4-stroke engines after 50 hours. (Offers 42% hydrocarbon reduction and 58% CO emissions reduction)
  • Faster starts: Its Diamondfire design concentrates spark energy, resulting in quick starts.
  • Increases power: It increases power by 6% to 12%, depending on the class of your engine class.
  • Better fuel efficiency: Improves fuel efficiency by 4% to 13% depending on your engine type.


  • The package has a 5K Ohm resistor.
  • It offers a universal fit.
  • Performs better in extreme conditions.
  • Ideal for professional racing vehicles.


  • It costs more than conventional plugs.

VERDICT: These plugs have a central copper core and nickel alloy body with a 5/8 hex for better conductivity. They are often used for most late Harley Davidson engine models and V-Twin motorcycle engines.

2. NGK Iridium IX DCPR7EIX Spark Plugs – Best for Harley-Davidson Twin Cam

These plugs have advanced spark plug technology and can withstand a lot of vibration and knocking. The NGK Iridium spark plugs would work best on Harley Davidson Twin Cam engines. When used, the spark plugs give a gain of up to 3 HP.

Each spark plug has an electrode made of iridium and is a quarter the size of a standard nickel electrode. It is only 25% smaller than a platinum electrode. The model’s reach is 19 mm with a gap of 0.031 inches and 12 mm threads at a 1.25 mm pitch. It also comes with a 5K Ohm resistor and a removable nut terminal.

These spark plugs provide superior electrical insulation characteristics and thermal-resistant properties. They also have better throttle reactions and instant ignition for improved engine efficiency.

Important Features

  • Anti-corrosion: The metal casing plating prevents the seizing and corrosion of spark plug threads.
  • Prolongs ignition system life: Its central electrode reduces voltage demand to extend the life of the ignition system.
  • Come pre-spaced: NGK Iridium IX DCPR7EIX spark plugs are pre-measured to work in various engines.
  • Improved performance: It provides an advanced wear resistance and has a high melting point for better performance.


  • Sparks at a lower voltage.
  • Greater durability with a hot flame.
  • Reliable power for stock engines.
  • Improves fuel efficiency.


  • Not perfect for bikes with modified engines.

VERDICT: NGK spark plugs / iridium spark plugs have an iridium alloy tip, copper core, and a fine wire center electrode. They also have a small diameter and reduce voltage requirements, ensuring your engine’s performance and longevity.

3. ACDelco 41-993 Professional Iridium Spark Plug – Best for Gas-Fueled Engines

ACDelco 41-993 Iridium Spark Plug is a top quality spark plugs for Harley motorcycles. It is more dynamic and provides a higher level of wear resistance than platinum and other conventional spark plugs.

The structure of iridium makes it very responsive at enduring extreme pressures and temperatures. Its endurance keeps the sparks from getting damaged due to engine combustion, making it the number one choice for a gas-fueled engine.

This spark plug has a one-piece suppressor seal that blocks off any radio frequencies affecting your bike’s electronics. Also, it features fine-wire electrodes that provide a great cold start and fast acceleration.

Important Features

  • Better fuel ignition: It has a fine iridium wire electrode that helps to improve fuel ignition. The wire also burns carbon deposits at the plug’s tip as they form, improving the fuel economy.
  • Long electrode life: It has suppressor sealing meters that seal against combustion leaks for a longer electrode life.
  • Improved engine performance: Iridium provides smoother engine performance with better stability.
  • Better reliability: The spark is resilient and can withstand harsh engine elements. It has been tested under temperatures of up to 4,000F and pressures of up to 2,000psi (3,000psi in some engines).


  • Has an improved ignition lifespan.
  • It operates with a lower voltage.
  • Provides a quick acceleration.
  • It is highly durable.


  • It might be a bit hard to install.

VERDICT: ACDelco manufactured this plug for smoother and improved engine idle stability. It uses low voltages to improve the ignition system performance.

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4. Briggs & Stratton Spark Plug Platinum – Best for Four-Stroke Engines

Briggs & Stratton Spark Plug offers quicker accelerations under all conditions. It is specially designed for quality performance in Harley Davidsons powered by 4-stroke engines. This plug primarily applies to most Briggs & Stratton Vanguard engines, L-head models, and select OHV engines.

Upgrading to Briggs & Stratton Spark Plug will improve starting, making your engine more consistent and efficient. The plug also provides steady idle, increased ignitability, and longer plug life.

This Platinum spark plug is better as it suppresses electrical noise interference using a SAC 9 resistor element. Its TinTac coating with gold shell also reduces seizing in heads and corrosion for better durability. You can get at least 100,000 miles of usage without wearing and tearing.

Important Features

  • Improve fuel economy: Ensures that gasoline burns more efficiently, thus improving fuel economy.
  • Reduced fouling: Its new projected core nose is uniquely created for peak performance without fouling.
  • Resists corrosion: The center electrode has a platinum pad that reduces gap erosion and makes the plug last longer.
  • Increased ignitability: A tapered ground electrode with a smaller diameter increases ignitability.


  • Designed to exact OEM standards.
  • Solves carbon buildup problems.
  • Ensures consistent spark.
  • Saves the engine from damage.


  • It does not have the best conductive material.

VERDICT: These spark plugs have a tapered ground electrode with a copper core to provide high-level engine efficiency. But ensure they fit your Harley Davidson engine as they are made for Vanguard engines, L-head models, and select OHV engines.

5. Denso PK20TT Platinum Spark Plug – Best for Minimizing Engine Misfires

Denso PK20TT Platinum Spark Plug works well with Harley-Davidson Twin Cam and Sportster bikes. It has a 0.43-inch platinum center electrode and a 0.43-inch titanium-enhanced alloy surrounding it. The alloy coating minimizes the tip’s erosion and seizing to improve its durability.

With its optimum spark performance, this plug can work over 60,000 miles without wearing out. Also, it minimizes engine misfires to increase your bike’s acceleration and fuel economy.

The Spark Plug has a taper-cut ground electrode that improves ignitability and reduces quenching. Its U-shaped groove will generate flames at lower voltages, producing an ignition without increasing the gap size.

Important Features

  • Better engine performance: The twin-tip design ensures efficient combustion for improved engine operation.
  • Thermal conductivity: Provides exceptional strength and thermal conductivity due to its purified alumina powder insulator.
  • High-quality: Denso PK20TT Platinum Spark Plug is 100% pre-fired to ensure they are high quality and durable.
  • Durable: The spark has platinum on both the ground and center electrode to make it last longer.


  • The electrode has efficient cooling.
  • Provides reliable performance.
  • Improves fuel efficiency.
  • Eliminates carbon buildup in the engine


  • May not fit all Harley Davidson motorcycles.

VERDICT: This spark plug has rolled threads that prevent seizing or cross-threading during installation. Also, the patented design will improve ignitability and extend its reliability and shelf-life.

What to look for while buying a spark plug for your Harley Davidson

Changing your motorcycle spark plugs to achieve the best performance is always a good idea. You need to consider the following factors before purchasing a spark plug for your Harley.

Plug material

Different plug materials function differently. When picking a plug based on its material, you should consider its durability, reliability, price, and efficiency. Here are the different spark plugs available:

  • Iridium Spark Plugs: Iridium is the hardest spark plug and probably the best plug material with a fine center electrode. It has a longer lifespan, improves acceleration, and provides more engine power. However, it is rare and more expensive than other spark plug materials.
  • Copper Spark Plugs: These are the most common standard plugs, since copper is one of the best electricity conductors. Copper spark plugs rarely overheat, making them more durable and responsive to high temperatures. These plugs are inexpensive and ideal for people working on a budget.
  • Platinum Spark Plugs: These platinum-tipped plugs are usually more durable and costly than copper plugs. The platinum plugs are of two types; single platinum spark plugs, which are less conductive than copper but more expensive. And, double platinum spark plugs have double plates at the tip, giving better endurance than copper.

Type of Engine

Different engines may have specific needs, especially for heat ranges and how far a plug goes into the combustion chamber.

Also, some engines function better with iridium or platinum plugs, which reduce mileage and emissions. Others, however, prefer steel or copper, which improve performance and offer great fuel efficiency.

You can visit an extra-fuel mileage shop if you cannot find the best plug for your engine type. They will recommend the best spark plug to improve your Harley’s performance.


A spark plug gap is a distance between the ground and center electrodes. Therefore, getting a plug with the correct size is crucial to ensure no engine misfire.

Usually, big gaps require big sparks and, consequently, bigger voltage to make the spark. On the other hand, small gaps need small sparks and a small voltage to cause the spark.

Many spark plugs come already gapped; however, you can optimize the spark plug gap by yourself. Though the process may be tricky, ensure you do not exert force on other plug parts except on the ground electrode strap.

Heat Range

Plugs with a hot heat range will not work on a higher RPM bike, and cold-type plugs will not work on lower RPM bikes. Also, very hot plugs can cause pre-ignition, while very cold plugs wear out quickly.

A plug’s heat range is typically imprinted on its side. Longer distances signify hotter plugs, while short distances signify colder plugs.

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The reach determines how far the plug reaches into the engine cylinder; it has to be the right length. One that is too short will not be effective, while a longer one may cause pre-ignition, hit the valves inside the engine, or even get jammed. To obtain a spark plug with the right size, check the thread of the original plug and go for a similar number.

Ground Electrodes

The more electrodes you have, the more durable your spark plug will be. Once one electrode burns out, you will still have the others to support the combustion. Also, multiple electrodes can improve flame propagation, especially if the engine is high compression.

Another thing to consider would be the electrode size. Larger electrodes have more reliable low-end performance. A smaller electrode produces hotter sparks and higher top-end performance, but they erode more quickly. Pick larger electrodes above 0.5 mm for a cruiser and smaller electrodes of around 0.4 mm for sports bikes.

Frequently Asked Questions

What are the benefits of using a good spark plug for Harley Davidson?

Using the best spark plugs for your Harley Davidson offers several benefits such as improved acceleration, more engine output, better engine starts, improved fuel economy, and more.

How often should you change spark plugs?

Depending on your model and the distance you travel, the recommended time to change your Harley spark plugs is between 15,000 and 16,000 miles.

How do you know if your Harley Davidson needs new spark plugs?

When your bike starts to run rough, loses power, or sputters, it’s time to check or replace the existing plugs. It’s important to check them regularly for safety.

How many spark plugs does a Harley have?

A Harley usually has four spark plugs—two on the left side of the bike and two on the right side.

Are iridium spark plugs better for motorcycles?

Yes, they are. Iridium spark plugs are considered six times harder and eight times stronger than platinum.

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What are the best spark plugs for harley davidson motorbike? We hope you now have your answer. Our picks are the five best spark plugs for your Harley Davidson, and it’s up to you to choose the most suitable option for you. 

Here, it’s important to assess the material of the spark plugs before you choose a particular option. It would help if you also considered the distance you travel and how much you’re ready to part with.

If you want to know which are the best Harley spark plugs among the five of them, every brand is outstanding.

All you have to do is use this guide to choose the best one for your bike and enjoy high-performance journeys and adventures.

joshua mattie

Joshua D. Mattie

My motorbike addiction began with 50cc at 5 years old. I rode motocross as a teenager & into my 20's when I worked as a mechanic. This helped me to see the light—sportbikes & cruisers became a passion. Now I'm building BikersRights to be the #1 resource for everything on 2 wheels!