Best Spark Plugs For Harley 103 – Top 5 spark plugs of 2021

Best spark plugs for Harley 103

During our routine inspections, it is easy to figure out if the tires need an upgrade or whether the oil needs to be changed. Often, riders forget that spark plugs are just as important. But, if you are reading this, we are sure you are not one of them. This article is dedicated to helping you find the best spark plugs for your Harley 103, a motorcycle that’s stolen our hearts!

The basics of spark plugs

Spark plugs work by providing the “spark” that makes motorcycles jump to life. They do so by igniting the air-fuel mixture using high-voltage electricity. If a spark plug is working fine, you will be able to start your motorcycle easily, control it well, and accelerate it as per your requirements. If it is not working well, there will be visible signs of distress.

Having said that, you should know that these signs may not always be obvious. Thus, if you have a doubt that your spark plugs have gone bad or might go bad soon, you should conduct a small inspection. Look out for the following:

  • Black carbon build-up
  • Exposed plug wiring 
  • Cracking wiring

These are physical signs that your spark plugs have worn out and need replacement. Other signs include rough idling, difficulty starting, and acceleration problems. A few may also hear a rumbling sound while riding their Harley 103. 

If you are doubtful, having a mechanic do a thorough check is always a good idea.

The importance of choosing the right brand

Once you have established that you need new spark plugs, you will move to the next part of the process – choosing the right spark plugs. There are many brands that sell good spark plugs for Harley 103, which makes it confusing. Are they all the same? Can you pick any brand? Not really. Just like in the case of everything, the brand you pick is of a lot of importance. Some of them have better spark plugs than others in terms of performance and durability. If you are worried because you are not sure which brands these are, go through the next section. We have listed out our favorites!

Best spark plugs for Harley 103 – Editor’s choice

Here’s our list of the top 5 spark plugs in 2021 for your motorcycle. Read on, compare, shortlist, and shop!

1. NGK Iridium IX DCPR7EIX – Set of 2

NGK Iridium IX DCPR7EIX – Set of 2NGK spark plugs are ruling the market at the moment with their top quality and reliability. Most users rush to buy NGK spark plugs due to these reasons as well as the ones we have mentioned below:

  1. These iridium spark plugs have been designed for 1999 to 2016 Harley Davidson vehicles.
  2. Their core material is nickel while their electrode is made of iridium.
  3. Once you install these spark plugs, you will notice that the motorcycle fires up instantly and rides very smoothly.
  4. The spark plugs are designed for better performance and acceleration.
  5. Cold starting is a breeze with these spark plugs. Moreover, you can run the engine very smoothly even at low RPM.
  6. They have an anti-corrosion coating – the trivalent metal plating.
  7. You won’t have to worry about flashovers anymore because of its corrugated ribs that prevent them altogether.
  • Improve throttle response
  • Easy to install
  • Perfect OE replacements
  • Triple gasket seal avoids leakages
  • Expensive
buy @ amazon

2. E3 Spark Plugs – E336

E3 Spark Plugs – E336E3 feels like a new name amidst Bilstein and NGK but trust us, it is not! It is actually quite popular in the motorcycle world because its spark plugs pack quite a punch. Let’s find out more about this particular model.

  1. They are a universal fit, which means they will easily fit your Harley Davidson.
  2. They are ideal for bikes used in racing and power sports.
  3. If you ride your motorcycle in cold temperatures very often, you will love these spark plugs. They have been designed specifically for this purpose. So, it is needless to say that cold starts are easy. It handles heat just as well too.
  4. They also have a yttrium-enhanced alloy that works to improve durability by significantly reducing the side-wire temperature.
  5. The thread diameter of these plugs is 12mm while the reach is 0.750 inches.
  6. Their core material is copper.
  • Does well in cold and heat
  • Lower emissions
  • Fast starts
  • Limited lifetime warranty
  • No significant improvement in the performance of the vehicle
buy @ amazon

3. NGK Spark Plug – 6046

NGK Spark Plug – 6046Here’s another NGK spark plug with a fine iridium tip that you might like. It is designed for a boost in performance and focuses on endurance. Below are a few more details:

  1. This is the perfect choice for your Harley because it offers better throttle response, easy ignitability, and anti-fouling.
  2. Its fine wire iridium tip measures only 0.6mm and ensures a stable spark.
  3. Electrical quenching will not happen here because of the tapered ground electrode.
  4. The spark plug has a long insulator nose to keep fouling away. Its corrugated ribs work simultaneously to avoid flashovers.
  5. It is anti-corrosive and has anti-seizing properties thanks to its trivalent metal plating.
  6. You don’t even have to worry about combustion gas leakage because the triple gasket seal is very strong.
  • Pre-gapped
  • Faster starts
  • Better fuel economy
  • Expensive

buy @ amazon

4. Iridium Performance Spark Plugs – Harley 6R12

Iridium Performance Spark Plugs – Harley 6R12This set of 2 spark plugs is sold in pairs and will fit your Harley 103 with ease. Installation is also straightforward, which means that you won’t have to worry about spending hours on it. Let’s find out more:

  1. This is an iridium spark plug, requiring low voltage due to its small size. This is a significant advantage over standard spark plugs.
  2. You will enjoy extended service life and hotter spark with these plugs.
  3. They have an excellent gold coating that avoids corrosion.
  4. The thread diameter of these spark plugs is 12mm while the reach is 11/16 inches.
  5. This is a projector insulator type plug with a removable terminal nut.
  • Better torque and horsepower
  • Instant starts
  • Better performance
  • Throttle response is not great

buy @ amazon

5. NGK 6046 DCPR7EIX Iridium Spark Plug 

NGK 6046 DCPR7EIX Iridium Spark Plug We shall round off our list with another spectacular product from NGK. This is an iridium spark plug as well and it has the following features:

  1. It has a laser-welded fine iridium tip that measures only 0.6mm. It requires less voltage to start and is very durable.
  2. You will enjoy a consistent spark with these spark plugs.
  3. It has a tapered ground electrode that removes quenching.
  4. Once you install these spark plugs, you will see an improvement in performance, throttle response, and ignitability.
  5. You won’t have to worry about fouling because it has a long insulator nose.
  6. No gas leakages or flashovers to think about thanks to its trivalent plating and triple gasket seal.
  • Smoother idling
  • Quick starts
  • High durability even in heat
  • Long insulator
  • Expensive
buy @ amazon

People also ask

We shortlisted a few FAQs on this topic and answered them in this section to clear your doubts.

1) What is the best spark plug for Harley Davidson?

Our vote would go to NGK but if you are looking for budget options, E3 is a great choice.

2) Can spark plugs increase horsepower?

Yes, they have the ability to increase horsepower.

3) What is the best spark plug for performance?

NGK IX is the best spark plug for performance.

4) Are Harley Davidson plugs pre-gapped?

Yes, they come pre-gapped.

5) NGK vs Denso – Which is better?

NGK spark plugs are said to be better because they are more durable, offer better spark, and improve performance.

6) What happens when the spark plug gap is too wide?

The engine won’t accelerate seamlessly and you will have trouble with the spark.


Harley Davidson motorcycles are built for high performance and durability. It is important that you do justice to them by buying the right replacement spark plugs when the time comes. We hope this article gave you clarity on the topic. Enjoy shopping for your new spark plugs and get back to us if you have any more questions. 

Francis Ceron

About Francis Ceron

Did you know the major cause of car failures are due to spark plugs. At sparklplugs guru you wil find all the necessary reviews, guides and facts to improve the performance of your vehicle and have a smooth functioning.

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