Best Spark Plugs for Harley Davidson – Reviews

1. NGK DCPR7EIX – Iridium Spark Plugs for Harley Davidson

Are you searching for the best spark plugs for harley sportster? NGK is one of the oldest names in spark plugs, and their products are always a safe bet. The DCPR7EIX is an iridium electrode model which contributes to its excellent reputation for reliability and performance. Compared to a standard electrode, the spark-gap performance of an iridium electrode has improved conductivity. This allows for a smaller electrode surface area and a hotter spark and even a weaker ignition system to still provide optimal performance for your bike.

The electrode on a sparkplug is analogous to a garden hose. The smaller the tip, the more forceful the spark will be for a given voltage or amperage. Thus, the smaller electrode of the NGK Iridium IX DCPR7EIX is a great way to guarantee optimal performance for your Harley Davidson.

This Isn’t The Best Option for a Performance Setting

While the NGK Iridium IX DCPR7EIX is unquestionably a great OEM replacement plug for your Harley, it is not the right choice for all applications. Because of the comparatively small electrode area, this plug is designed to produce a hot spark with a smaller flame-surface area. This means that the flame surface will be less likely to propagate in higher performance engines. This can have two impacts.

First, in a high displacement engine, such as one that has been bored or stroked, this plug may have a difficult time producing sufficient spark area to properly ignite the intake charge.

Further, this plug may experience detonation in extremely high-compression racing engines. Thus, if you want a fantastic OEM replacement plug for your mostly stock bike, this is a great option. However, if you are pushing the limits of power, you may want to look elsewhere.

2. E3.36 – E3 Spark Plugs for Harley Davidson Twin Cam 88

In contrast to the NGK mentioned above, the E3 Spark Plug E3.36 is a spark plug that can punch well above its weight in a tuned or modified engine. Unlike the iridium plug of the NGK, the E3 uses a yttrium-enhanced alloy for its electrode surface. What does that mean in plain language? This formulation has two main impacts. First, yttrium possesses greater thermal transfer properties, meaning this plug will stay cooler in higher-performance applications.

What’s the Deal with Heat?

In extremely high-compression engines, spark plug temperatures can become high enough to melt the electrode, increase the temperature of the compression charge, or even cause detonation. If you choose the wrong plug for the job, your spark plug can begin to function as a glow plug instead. This will combust fuel at the wrong moment, impacting performance or destroying your engine. In testing, the metallurgy of this plug has been shown to result in temperatures up to 8% cooler.

More Surface Area = More Flame

The other key advantage of the E3 E3.36 plug is the increased surface area. Unlike a traditional plug which has only one electrode surface, the E3 has three arranged in a triangular configuration. Thus, rather than having an offset flame trajectory path, the three electrodes of the E3 spark plug allow for symmetrical combustion propagation leading to a more robust flame front and more even combustion distribution. This increase in the flame surface area makes this an ideal plug for a higher performance application. If you have a higher compression engine, a larger displacement setup, or even a pure race engine in your Harley Davidson, this is a fantastic plug to use.

The Price is Right Too

Perhaps the most impressive aspect of the E3 is the price. Often, high-performance spark plugs can cost multiples of the price of their more pedestrian counterparts. However, this isn’t the case with the E3. Despite the exotic formulation and high-performance credentials, this plug is on-par price-wise with OEM replacements. For any biker who is serious about performance, this is one of the best spark plugs for Harley Davidson EVO. Get harley spark plugs with great quality at amazon!

3. Denso IXU22 – Best Spark Plugs for Harley Davidson Sportster 1200

Different applications call for different spark plugs. That is why this overview is not really a review at all, but rather an analysis of the strengths of each plug. While the NGK is an excellent performance plug for a stock application, and the E3 is a go-to plug for modified engines, the Denso 5308 IXU22 is the right choice for a stock bike that lives lower in the rev-range.

Designing a spark plug is often a lesson in compromises. It is impossible to design a plug that performs optimally in all circumstances. Thus, designers are often tasked with designing a plug that is at home in specific rev-ranges. For lower revving applications, this Denso is a fantastic choice.

Contrasting Electrode and Cathode Sizes

As explained above, smaller electrodes tend to result in a hotter spark. This is excellent for high-RPM applications but can result in less power lower in the rev-range. To combat this, Denso designed a plug that has a 0.4mm iridium electrode but a significantly larger cathode. This unique combination leads to a plug that has adequate spark heat for maintaining ignition at high RPM’s, but also provides sufficient surface area for low-RPM grunt. Simply put, this is a spark plug designed for torque.

The Shape Matters

The contrasting sizes are not the only aspect that lends this plug to low-speed cruising. The ground electrode has an electro-etched U-groove that increases the speed of the flame growth during periods of lower intake velocity. Think of it as a ramp for the spark. The other advantage of this design is that the shape of the electrode promotes more efficient cooling of the plug itself. Thus, this plug will continue to provide reliable and detonation-free performance for years.

While this plug is unlikely to win any drag races, that isn’t its intent. Rather, this is a spark plug designed specifically for the best cruising performance at low-RPMs. Thus, if you are looking for a plug to keep your Harley Davidson running its best while cruising the town, this is an excellent choice.

4. Champion 810 – Spark Plugs for Harley Davidson Road King

Many people think that you only need to replace spark plugs if your engine isn’t running properly, and that spark plugs have little impact on the performance and characteristics of the bike. However, this is a gross oversimplification.

Having the proper spark plug can have a significant impact on the performance reliability of your Harley Davidson. If you are looking for a spark plug that prioritizes reliability over peak performance, the Champion 810 is a plug to consider.

More Area Equals More Reliability

The ignition system of an engine is normally fairly simple. In most cases, an ignition system will consist of a distributor (or its electronic equivalent) that tells each plug when to fire. Then, you have a coil or coil pack that produces the necessary voltage to fire the plug. Finally, you have the plug itself that sparks, igniting the fuel.

Being interconnected, the spark plug will have an impact on all of these components upstream. Although a smaller electrode will produce a hotter flame and result in higher peak performance, it also puts an increased load on the coil. By minimizing the electrode area, the current is increased, and the coil is asked to transfer more current for each ignition pulse. In the short term, this is not normally an issue. However, this effect can weaken or destroy a coil or coil pack over time.

Made wisely

The Champion 810 was designed with this in mind. It uses a particularly large 0.7mm electrode and a 1.0mm grounding surface. Thus, in terms of the electrical contact area, there are few plugs with more. This design reduces the intensity of the spark generated by the plug. While this may slightly impact top-end performance, it also significantly reduces the strain on the ignition system. Thus, for a long-distance or commuter bike, this plug is a superb choice.

5. Bosch WR8DP+ – Spark Plugs for Harley Davidson Evo

While most spark plugs have a specific goal or purpose in mind, not all of them succeed in achieving it. The Bosch 4018 WR8DP+ is designed as an OEM-replacement spark plug for Harley Davidson Evo engines. In keeping with a stock-replacement philosophy, this is not an aggressive plug and is tuned primarily for low-RPM performance. However, the result leaves a fair amount to be desired.

Not All Metal is Equivalent

The first issue with the Bosch WR8DP+ is the metal composition. This plug uses a platinum-yttrium alloy for both the ground point and the electrode. While this composition was cutting edge decades ago, this is an old-fashioned approach from today’s perspective.

Compared to modern plugs, platinum-yttrium plugs tend to demonstrate higher electrical resistance, resulting in a weaker flame and more work for the coil. Further, the heat dissipation qualities of this alloy are comparatively poor. Thus, the spark performance of this plug will be inferior to many modern units, especially over prolonged use.

The Spark Has No Direction

The secondary issue with this plug is the shape and size of the electrode. The modern trend is to use extremely fine electrode points to increase spark force. In contrast, the electrode of this Bosch unit is extremely broad. Worse yet, it is almost completely flat.

Thus, while a modern plug will have a focused spark encouraging an even flame front, the arc-pattern on the Bosch was unpredictable. Because of the relatively featureless electrode, there was no consistency in the propagation of the flame front. This can decrease performance and make an engine harder to tune.

There was a time that this plug would have been acceptable. Yet, with modern advances, this has become one that is best to avoid.

6. Orange Cycle Parts – High-Performance Spark Plugs for Harley Davidson

It would be ultimately pointless to spend too much time analyzing the performance characteristics of this plug because that was never the focus of the design. In function, this is a fairly standard Iridium plug with a 0.5mm single-point electrode. Thus, this is an excellent OEM-replacement plug that will serve well in any relatively stock application. It won’t perform exceptionally well in any context, but it won’t disappoint either.

Looks Matter

The highlight of this plug is the appearance. With its distinctive gold-and-black theme, this is unquestionably an attractive plug. Speaking honestly, many modifications to motorcycles are done more for looks than outright performance. There’s nothing wrong with that. As spark plugs go, this is a beautiful one.

The simple question becomes whether or not the cylinder head design of your bike allows for the plug to be seen, and whether you run a “shorty” insulation boot. If you do, then there’s no reason not to enjoy adding a little extra bling to your block.

The Gold Has Its Price

The only downside to these plugs is the price. For a non-performance-oriented plug, they are unquestionably expensive. This is doubly true when you consider the fact that the gold plating has no real performance advantages. However, they are a distinctive addition to your bike that will provide adequate performance at an ultimately reasonable price. Thus, if gold strikes your fancy, make it so.