Best Spark Plugs for Harley Davidson [Reviews & Guide] in 2023

Finding the best motorcycle spark plug is almost next to impossible, especially when it comes to engines of brands like Harley Davidson. To match their reliability, the spark plugs need to be of high-quality too. Therefore, we are going to help you find the best spark plugs for Harley Davidson to reduce your time for gambling.

In the review of the 7 best Harley spark plugs, we will cover all the crucial points such as their material, size of electrode, voltage requirements, etc.

Top 7 Spark Plugs for Harley Davidson

• Best spark plug for motorcycle- DENSO # 3297 Iridium LONG LIFE Spark Plugs
• High performance spark plugs for Harley-Davidson- ACDelco 41-993 Professional Iridium Spark Plug
• Best ngk iridium spark plugs for Harley-Davidson-  NGK IRIDIUM IX Spark Plug LTR6IX-11
• Best spark plug for motorcycle- E3 spark plugs for Harley-Davidson
• Best spark plugs for 883 Sportster- NGK (6046) DCPR7EIX Iridium IX Spark Plug
• Best spark plugs for horsepower- NGK 7090 BKR5E G-Power

7 Top-Rated Spark Plugs for Harley Davidson Review

1. NGK IRIDIUM IX Spark Plug LTR6IX-11

Material & Durability

NGK produces the top-rated spark plugs for every type of automobile vehicle, that too with top-quality materials infused with unlimited benefits.

The core material of these NGK spark plugs is iridium, and the electrodes are fine wire-centered, which is proven to be six times stronger than traditional copper electrodes.

Whereas the high melting point of iridium alloy makes them the best Harley plugs for their respective engines. Once you place them, you won’t have to replace them till you travel 100,000 miles.

Performance

Iridium build of these best spark plugs makes their electrode compact that in return makes the spark plugs perform the best in low voltage.

Hence, not only are you getting high performance, but also saving on some fuel. Moreover, the plugs will make Harley engines run, have smoother acceleration and idling.

Installation

To install the plugs in your Harley Davidson bike, you need to check the electrodes’ pre-gap size. Yes, these NGK spark plugs come pre-gapped.

If the gap doesn’t match for a little bit, you can customize it yourself or call a mechanic to do it for you and get them installed.

Pros:

• Long-lasting and durable build
• Improves the engines’ speed
• It comes pre-gapped for hassle-free installation
• Enables faster bike starts

Cons:

• It costs more than traditional plugs

Recommendations for which model:

These NGK Harley plugs will fit in varieties of Harley motorbikes, starting from 1999-2016. They are versatile and come pre-gapped; however, you can always adjust the gapping.

2. NGK Iridium IX DCPR7EIX Spark Plugs for 1999-2016 Harley Davidson Twin Cam

Material

Another best spark plug pair from the evergreen NGK is again made from robust iridium alloy. They come in ‘powerful pairs’ and are made to fit all the models of Harley Davidson.

There is nothing new to tell about iridium regarding its durability for providing your engine with long-lasting, unlimited power.

The center electrode is also made from iridium to obtain a high-melting point and heat-resisting capability that helps them survive through overheating.

The outer part is multi-shelled for prevention against corrosion.

Performance:

Performance-wise, this pair of best NGK spark plugs leave everyone behind. You will ultimately enjoy an additional 3HP with its latest design. With that addition, any Harley Davidson motorbike shall run faster.

Moreover, compared to nickel or platinum electrodes, the 25% reduction of these iridium electrodes requires less voltage for optimum performance. Your bike will start even faster and run smoother than ever.

Pre-gapped electrodes

For hassle-free placement, these iridium spark plugs for motorcycles come pre-gapped. If you pre-analyze the gaps for your bike’s requirement, then you won’t have to fall into a fitment issue. However, the gaps are slightly adjustable if anyone needs them.

Pros:

• Has three times additional HP
• Multi-shelled to prevent rusting
• It comes pre-gapped for easy placement
• Needs less voltage
• Electrodes are 25% smaller for high-efficiency

Cons:

• It does not fit the latest harley Davidson

Recommendations for which model:

These are the best spark plugs for horsepower to fit in every Harley Davidson motorbike manufactured from 1999 to 2016.

3. ACDelco 41-993 Professional Iridium Spark Plug

Material

Another iridium spark plug set, but from a different brand, AC Delco. One of the cost-effective spark plugs till now where you get 8 pieces of spark plugs in less than 20 dollars.

These iridium spark plugs for Harley Davidson are valued for money to obtain maximum power for your motorbike’s engine.

The electrodes are fine-wired and made from the same material, iridium.

Cost-saving

The upfront cost of these spark plugs is low, but they help save your cost even further by saving fuel for you.

The fine wire electrodes enable faster fuel ignition that even burns away the carbon buildup from the electrode tip. Hence, you will enjoy the same mileage with lesser fuel required.

Performance

AC Delco Iridium spark plugs offer a high-performing engine with smooth acceleration and stable idling. The plugs and their electrodes with high-melting points obtained from the electrodes prevent wearing due to overheating.

Therefore, you can enjoy long-lasting support from these best performance spark plugs.

Protection

These spark plugs also have a suppressor seal meter that blocks away from the radio frequencies, which deteriorates other car components. Moreover, the meter also protects against combustion in the electrodes.

Pros:

• Has self-protective measures
• Made for longer-lasting performance
• Prevents electrode combustion
• Very cost-friendly
• It has a high melting point

Cons:

• They are not made for every motorbike.

Recommendations for which model: You can expect these AC Delco’s best spark plugs to get fitted in Harley Davidson motorbike. You may need to match the spark plug gap for your model to see if it fits there or not.

4. DENSO # 3297 Iridium LONG LIFE Spark Plugs

Design

In the history of spark plugs, DENSO was the very first manufacturer to bring up iridium spark plugs in the market to cope up with modern high-tech engines.

Now, almost every spark plug brand has changed with customers’ demand for their durability and upthrust performance.

You will encounter a 360 degrees laser-welding process in these spark plugs that protect the electrodes from wearing and breakage even in the toughest driving condition.

This design was patented in the USA and Japan by Denso. It is one of the recommended spark plugs for modern engines, such as the Harley Davidson.

Performance

After reading about the history of design, you might have already gotten an idea of how reliable performances you will get from DENSO. The state and fusion of technology provide unmatched performance, fitment, and dependability to your motorbike.

These Harley spark plugs will provide improved fuel economy, a powerful engine without a misfire, and greater acceleration so that you can enjoy more miles without any obstacles.

Pros:

• Made of iridium for durability
• Has 360 degrees laser-welding
• Electrodes can survive the hardest conditions
• Provides better fuel economy
• The engine does not misfire

Cons:

• Pre-gaping might need adjustment.

Recommended for which model: These laser-welded iridium spark plugs can fit into any Harley Davidson motorbike as they are designed to fit all the modern, high-performing engines and have an art of better fitment for them.

So, make sure you know your engine’s requirements well before buying them

5. E3.54 E3 Premium Automotive Spark Plugs

Design

These premium-quality spark plugs are designed to fit into some specific engines, and unfortunately, not for all! E3 spark plugs for Harley Davidson are pre-gapped exactly required for your engine’s compatibility and performance needs.

These E3 spark plugs are considered best for sports bikes to contribute to high-speed racing in the past. Also, the precious diamond fire electrodes are protected by three legs on top of the shell.

Performance

We won’t be able to end, once we start talking about the E3 premium spark plugs’ performance.

Firstly, it serves great speed to the engine, and the ground electrode design allows quicker combustion through excellent heat transfer sparks to burn the air-fuel mixture more efficiently.

As a result, fuel economy enhances without compromising performance.

Moreover, there will be no carbon/ oil-fouling buildup around the electrodes for a better lifespan of the plugs and the least maintenance.

E3 guarantees users that these plugs will last up to 13 years and give a100,000 miles warranty. You can also contribute to the environment with them, as these plugs will extensively reduce the emission of hydrocarbon gas.

Pros:

• Reduces carbon build-up and exhaustive gas emission
• Provides high-speed to the engine
• Improves fuel economy
• Has 13 years of warranty
• Fuel burns efficiently

Cons:

• Since, they have specific sizes, so all the motorbikes may not fit them well.

Recommended for which model: These amazing spark plugs are meant for high-speed racing cars and bikes. So, if you are looking for spark plugs for your Harley Davidson sports bike, these E3 premium spark pl

6. E3 Spark Plugs Power sports Spark Plug Each

Design

These E3 spark plugs are designed with copper as a core material for excellent heat transfer that enables faster ignition.

The design consists of Yttrium-alloy that reduces side wire temperature by 8% than other traditional wires to gain durability and reduce pre-ignition.

E3 has designed their spark plugs with colder heat ranges to balance out with fast, sports-type motorbikes. Even in the hardest journeys, the engine won’t get harmed by these spark plugs at all.

Performance

You will enjoy years of benefits with these good spark plugs in the market. They already come pre-gapped for faster and easier fitment in your motorbike.

Moreover, you can ‘go green’ with these spark plugs with significantly reduced hydrocarbon exhaustion into the atmosphere.

According to the manufacturer, E3 plugs will also carry the engine’s optimal performance for 13 years or more.

Pros:

• Provides more power to the engine
• Longer life of the engine
• Improves fuel efficiency
• Reduces foul gas emissions
• Very durable and long-lasting

Cons:

• Price is a bit high

Recommended spark plugs for which model: The spark plugs have a universal fit with a thread diameter of 12mm and Hex size of 5/ 8 inches.

So, if your Harley Davidson model falls into this specification, you can undoubtedly go and enjoy a high-speed racing experience with these spark plugs.

7.Briggs & Stratton Spark Plug Platinum For OHV Engines 5066K

Material

The last high-performance spark plug for Harley Davidson we have is from Briggs & Stratton. The Briggs & Stratton spark plugs for OHV engines are made of platinum alloy.

When it comes to durability, platinum is the second most durable material after iridium in spark plugs.

They hold quite a sharp edge compared to conventional spark plugs and have a reputation for leading to 100,000 miles at most.

They have high heat tampering capabilities and remain hot for a longer time for which carbon and oil fouling melts away.

Hence, you don’t have to take the hassle of frequent cleaning and maintenance. Also, less carbon fouling means more life to the spark plugs.

Performance

Briggs has implemented platinum in their spark plugs for optimum engine performance with easy engine starting and less fouling. The ignition is done well for quicker sparks and faster starts without misfiring.

Also, this exclusive platinum is made to outperform with enhanced fuel economy and smoother acceleration.

Pros:

• Perfect fit for OHV engines
• Reduces engine misfiring
• Has high heat tampering
• Prevents carbon and oil fouling
• It lasts a very long time

Cons

• Very costly compared to similar spark plugs

Recommended for which model: These spark plugs are made to fit vanguard and intek OH engines. So, before you buy them, check well if they fit in your Harley Davidson’s OH engine or not.

About Screamin Eagle spark plugs

Screaming eagle plugs are considered one of the toughest of all with their double-platinum built, for which they fight corrosion and erosion for durable, long-lasting performance.

The ground electrode is V-shape to lessen shrouding and promote flame propagation, whereas the fine-wired middle electrode improves ignition to speed up the start of engines.

You can use these spark plugs for bike races where you need a high fuel-air mixture. The OE patented design always keeps up with easy placement on carburetors, exhaust systems, ignition systems and much more.

There is RCT technology to these spark plugs to prevent carbon and oil fouling too.

Best spark plugs for harley sportster

Best Sparkplugs for Sportster of Harley are the E3.54 E3 Spark Plugs for motorcycles. They are specifically made to fit into and push sport bikes to the fullest.

They have high ignition capabilities and serves great speed to the engine. The ground electrode design allows quicker combustion through excellent heat transfer sparks to burn the air-fuel mixture more efficiently.

Moreover, the electrodes are protected to survive through the toughest driving conditions and last longer. The manufacturer already warrants them to last 13+years, so you can think of how selective this harley sportster spark plug is.

HarleyDavidson spark plug gap chart:

Above, you can see the Harley davidson spark plug gap chart. For easy comparison, they have cross-referred with all the good spark plugs of almost all the brands. There is also screamin eagle spark plug cross reference, Autolite, NGK and many more.

Source:https://www.harley-davidson.com/us/en/shop/Screamin-Eagle-Performance-Spark-Plugs/p/31600106

High-performance spark plug wires for Harley Davidson- Screamin’ Eagle 10mm Phat Spark Plug Wires:

The best motorcycle spark plug wires are the Screamin’ Eagle 10mm Phat Spark Plug Wires.

These 10mm thick wires ensure a robust connection between the spark plugs and engines.

Hence, there will be no waiting for voltage getting transferred and hindered ignition. They are strong, so they won’t wear out. These are one of those high-performance spark plug wires for Harley Davidson.

Pulstar spark plugs for harley Davidson:

Another motorcycle spark plugs are made from patented plasma technology for your Harley bikes. Your bike’s performance will get enhanced in an instant once you install these in their socket. They are made in the USA with high-quality material for long-lasting usage.

How to choose the best spark plugs for Harley Davidson – Buying guide

How often should you change spark plugs on a Harley Davidson?

The spark plug is made basically for bikes. It improves the starting power, engine performance, and fuel economy of the bike. Usually, the spark plugs on a Harley Davidson should change every 30000 miles to ensure the start of the bike.

The best spark plugs for Harley Davidson also offer the opportunity of keeping the engine cool.

For ensuring and maintaining the top performance of the motorcycle, the installation and maintenance of an appropriate spark plug are required.

In the modern motorcycle, the spark plug should replace after every 15,000 miles to 16,000 miles.

Spark plugs do not see in the checklist like tires and signals, among others.

When the bike is running rough, sputtering, or even losing power, it is time to inspect or replace the spark plug. Spark plug replacement is necessary to ensure safety.

What is the benefit of iridium spark plugs?

Most of the spark plugs that conduct in vehicles today provide features of the copper core Centre electrode.

These best spark plugs for performance design provide the advantage of the good operating rates that copper offers with electricity, providing better services than any other material type.

It also provides the opportunity of transferring faster heat.

To protect it, it also comes with a nickel alloy covering because the copper offers a low melting point. It provides so many benefits with these are following-

1. Improve the Acceleration Profile

The high-performance spark plugs for Harley Davidson are iridium spark plugs that improve the vehicle’s acceleration profiles.

Anyone can notice an immediate change in the acceleration profile when they make a move to iridium spark plugs.

This benefit gets because the throttle operations have a faster response. Some miles on the older plugs may lead to instantly showing differences and feeling the differences.

They can create an original difference when you live in regions where it is important for getting up to highway speeds quickly for remaining safe.

2. Provides More Engine Power

Iridium spark plugs for motorcycles enhance the engine power that improves the performance of the engine. This benefit can be identified when it requires climbing steep heels or handling challenging driving situations.

This experience will be apparent and can be noticed behind the wheel to become more comfortable with the upgrade.

It offers more control because of navigation and gives a smoother touring ability. When there has a variable transmission equipped to the vehicle, the iridium good spark plugs provide more power.

But in the case of using manual transmission, it provides more power only when appropriate shifting to the road condition has occurred.

It is the best spark plug for horsepower. Harley spark plug torque support is very effective.

3. Offer Better Starts

The ultra-fine center electrode of iridium spark plugs for Harley Davidson provides many efforts for ensuring the possible best ignition experience.

If you upgrade to the iridium spark plug, the vehicle will start better. After making the upgrades, it creates an immediate enhancement in the starting characteristics of the engine.

The idling becomes more stable because there is so little dispersion in the position of the spark in this product.

If you would not want to let the engine idle for an extended period for the potentiality of damage, the roughness will occur with the standard plugs that appear to disappear.

4. Keep the engine cool:

The Iridium spark plugs keep the engine cool. It helps to transfer the excess heat from the ignition chamber of the cylinder to the cooling system of the engine.

If there have Iridium spark plugs, it will ensure the engine’s cooling during a long trip.

5. Improve the Fuel Economy

Iridium spark plug improves the fuel economy and allows fuel to burn more efficiently. iridium spark plugs may immediately enhance the city’s gas mileage or on the highway.

Most of the drivers may experience a 10 percent to 20 percent gain over the entire tank of the gasoline, though the rate of efficiency is not exceptionally high.

It is the great spark plug that increases an extra 4 to 8 miles per gallon if already having a high mileage rate.

6. Requires Less Voltage

The Iridium sparkplugs require less voltage than other spark plug designs. As the electric currents surge from the iridium spark plug, power generation does not require as much voltage.

That is because of the distinctive configuration involving a tiny electrode during the start-up process or when accelerating; saving energy means having a reserve to help control the diving experience.

You can identify less lag after pressing down on the pedal and fewer delays in the engine’s initial starting up. This benefit can get with the battery’s cold-cranking amps for ensuring having more power available in the months of winter.

7.More Durability

The best motorcycle spark plug is Iridium spark plugs that provide more durability. The strength of this spark plug assures a long-lasting installation when making the upgrade.

Though various manufacturers produce it, before the new units need service, you will always receive an average of 50,000 miles.

Some drivers may get 80000 miles or more than it. If you want to settle for a platinum or copper spark plug, you will obtain 50 percent of the life span. That is the reason why this item’s price essentially scales itself over time.

8.More Corrosion Resistance

The iridium spark plugs provide more corrosion resistance. When working in temperatures as high as 2,000 degrees C, Iridium is one of the most corrosion-resistant metals.

While melted salt and halogen are corrosive in the solid metal, it still works incredibly well in the engine compartment because of these characteristics.

That refers to have access to a highly reliable component that supports the overall performance of the vehicle.

About iridium spark plugs

Iridium spark plug is top-rated spark plugs and high-performance motorcycle spark plugs. It is called to be eight times stronger and six times harder than platinum.

Iridium good spark plug is the best in comparison with platinum and copper.

Iridium spark plugs offer exceptionally fine electrodes, though preserving outstanding wear characteristics.

It provides outstanding strength; iridium spark plugs may last up to 25 percent longer than equivalent spark plugs.

It features a fine wire center electrode and is designed to operate better electrical energy and increase firing efficiency.

Motorbike spark plugs facilitate the precious metal and are usually the most expensive.

It provides more durability, little visible deterioration, lower voltage long lifespan, and better overall performance like gas mileage, reliability.

The electrode material provides a high melting point. It has quicker acceleration and is better smoother than the normal copper spark plugs.

Though Iridium is harder, it offers better performance. Iridium spark plugs require less voltage to fire, resulting in more coil dwell time.

It facilitates more horsepower as well as is most conducive and perfect for the high-performance engine.

The iridium spark plug can make the higher quality of flame that promotes the more concentrated spark in the cylinder, and the spark plug is known for it.

It can easily be distinguished by a narrow electrode like the tip of a pen. Most of the iridium spark plug has a shaped channel on the electrode for preventing extinguishing.

Which is a better spark plug material, Platinum or Iridium?

Some factors should be considered to determine the better spark plugs, such as efficiency, durability, and reliability; by considering efficiency, durability, and reliability, the Iridium spark plug is much better than the platinum spark plug.

The iridium spark plug is more strong and hard than the platinum spark plug. The iridium spark plug may outdo the platinum spark plug.

Note: The Iridium spark plug is eight times stronger and six times harder than the platinum spark plug that facilitates a 700 degree higher melting power.

Iridium spark plug is longer lasting than platinum spark plugs. Iridium spark plug is up to 25 percent longer lasting than platinum spark plugs.

The platinum spark plug is less expensive than the iridium spark plugs. Iridium spark plug is a common choice for modern vehicles.

The platinum spark plug provides poorer performance than the Iridium. Platinum spark plug requires replacement every 60,000 miles, whereas iridium plug requires replacement after 80,000 to 100,000 miles.

Iridium spark plug requires less energy or voltage than platinum spark plugs.

The iridium spark plugs still have a longer lifespan and more durability than the platinum spark plug.

Do iridium spark plugs increase performance?

Iridium spark plugs increase the performance of the engine in case of power. The extra power becomes visible when the engine is climbing hills and offers a comfortable touring experience and driving.

The ultra-fine center electrodes of the Iridium Plug enhance the starting characteristics of the engine as well as ensure fast ignition.

It improves the acceleration of the engine that facilitates fast response to throttle operation.

The iridium spark plugs ensure both environmental and economic benefits because the gasoline-burning is efficient. It provides better engine response and a smoother engine. 

Spark Plug Gap 

To ensure the correctness of the gap or the gap is right is an important key to success. The spark plug gap’s correctness can be achieved by checking the spark plug through a standard spark plug gap tool.

The force needs to exert must be on the spark plug’s ground electrode strap while reducing or widening the distance.

Never should apply any force to the ceramic insulator of the spark plug center electrode or center electrode.

Another important rule is that throughout the spark plugs’ lifetime, you should never adjust the distance more than three times and in either direction never more than .008′′.

Another important rule that every user should be remembered is that unless this has already pre-set by the manufacturer, you should never reach .055′′ above the manufacturer’s tolerance.

Cross reference chart – metric to standard (mm to the inch)

mm	0.4	0.5	0.6	0.7	0.8	0.9	1.0	1.4	1.5	1.6	1.7
inch	.016″	.020″	.024″	.028″	.032″	.035″	.039″	.055″	.059″	.063″	.067″

What is Harley twin cam spark plug?

Harley twin cam spark plug is the best spark plug for Harley twin cam designed specifically for the enthusiast of performance. The good wire center electrodes provide more durability and a consistent, stable spark.

It helps to easily start that reduces fouling of the plugs as well as provides longer performance. Harley twin cam spark plugs offer an extremely high melting point that is a high-performance engine and perfect for high tech nowadays.

It also offers heat control and increases conductivity that delivers good wear characteristics. The Harley twin cam has longer life and support for the accurate control of the plugs’ heat range.

It also optimizes the performance of the plugs and adds to the longevity of the Harley spark plugs.

It is also able to exceed the designs of OE that offer dependable performance and maximum durability. Harley twin cam spark plugs improve better horsepower and fuel efficiency.

It provides improved ignitability, a more focused ignition, and faster fuel combustion. The spark plugs for Harley Davidson twin cam offer superior Anti-Seizing and Anti-Corrosion properties as well as triple seals that prevent leakage.

Screamin Eagle Plug Wires vs Stock

Screaming eagle plug wires increase the horsepower and performance of the vehicle. The screaming eagle park plugs are not much different than stock. Screaming spark plugs provide more spark in the firing tip of the spark plug. There have no worth the price difference among them.

There are some common symptoms of failing the screaming eagle plug wires vs stock, such as decreased power, acceleration, and fuel efficiency.

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Frequently asked questions

4 Best spark plugs for 883 Sportster

• DCPR7EIX Iridium Spark Plug.
• NGK 3932 DCPR7E Spark Plug.
• Autolite Spark Plug 4164.
• Spark Plug Harley RA8HC 6R12

How often should you change spark plugs on a Harley Davidson?

 When the bike starts losing power, running rough, or even sputtering, it should be needed to replace or inspect the Harley spark plug. In the modern type of motorcycles, the best spark plugs for Harley

 should replace after riding the motorbike every 15000 to 16000 miles for better engine performance and starting. 

Do high-end spark plugs make a difference?

High-end best Harley spark plugs may perform well and consistently, which helps preserve the engine’s designed efficiency. They will not make the engine run better than it did when it was new, but they will help it remain longer at that stage.  

What’s the best spark plug for performance?

The NKG 6619 Iridium IX Spark Plugs provide the best mix of fuel efficiency, high performance, dependability, and durability, so it belongs to the top pick in the spark plug comparison. The features of Iridium HD spark plugs provide high-quality spark plugs that facilitate a longer lifespan than platinum and copper spark plugs.

What colour should my Harley spark plugs be?

An experienced engine tuner may determine a great deal about the engine’s overall operation state by inspecting the color of the insulator firing nose. In general, a light tan or grey colour ensures that the Harley Davidson Spark plugs are running at the optimal temperature, and the engine belongs in good condition.

What does a lean spark plug look like?

The spark plug is turned white or clean, a typical symptom of the car running lean. Generally, spark plugs are a grey or brown color because of natural ignition. The excessive heat indicators on the spark plug and ground strap may indicate a lean mixture.

How do you clean sooty spark plugs?

You can use good quality spark plug wires for Harley Davidson wire spray-on plug cleaner or brush that is specifically designed for this ignition component for safely cleaning a spark plug. To chip off difficult deposits, you should also use a robust knife. It would be best if you never cleaned a spark plug with an abrasive or shot blaster.

What does a black spark plug indicate?

The Black spark plugs indicate a carbon-fouled plug as well as insulator trip and the electrodes’ dry soot. It can be occurred by a dirty air filter, unnecessary driving at low-speed, too long idling of the engine, or too rich fuel or air mixture. 

What causes carbon fouling on spark plugs?

Carbon fouling indicates a weak ignition, rich air-fuel mixture, or improper heat range like too cold. Carbon deposit is conductive, and it may generate a way for the misfire of the spark plug. An overly rich state generally causes carbon fouling, or the problem can lie with the air cleaner or carburetor.

What causes ash deposits on spark plugs?

Heavy concentrations of ash resulting from fuel additives and oil on the insulator nose on the ground electrode and in the field of scavenging area. The configurations of the ashes are loose to cinder-like. The ash can be deposited on the spark plug face and combustion chamber through alloying constituents, especially from engine oil.

How do I know if my spark plugs need changing?

Some symptoms indicate the need to change spark plugs, like the starting of the bike is hard, misfires of the engine provide poor fuel economy, the engine idle becomes rough, really loud the engine, and the light of check engine is on, and the bike struggles for accelerating. 

Conclusion

We have introduced you to the Best spark plugs for the performance of your Harley Davidson; now it’s your time to choose one. If you ask what the best spark plugs among the seven are, then all of them are excellent on their own.

You just need to guide yourself to buy the correct one for your motorbike and enjoy the optimum high-tech journeys all along the spark plugs life.

Source: Beginner’s Guide on Spark Plug Carburetor Setting by Tuning Matters