you will notice in the first picture by -AK- you can see the spark plug throat, that is the electrode and ceramic insulator and then space between the threaded material and the electrode/ceramic insulator. How far up inside the spark plug does that space go? A typical copper spark plug will last around 20,000 miles and most get changed at a major service (usually around 16,000 miles) but an iridium spark plug will be good for around 50,000 miles and you do see people running them to 100,000 miles with no issues. Allows the use of an extremely small diameter electrode (0.6mm) without compromising the spark plugs service life

NGK Spark Plug Upgrade Chart - NGK Partfinder

Not sure if this is because the old plugs were past their best or if the new ones are better. :dunno The machined quality of the genuine plug is far superior with a much smoother appearance from base to thread. If the engine is running dangerously lean the whole plug tip will be grey or white. If the temperature is over 850-degrees, pre-ignition may occur. Engine power will be reduced and you risk piston damage. however, if the plug is too hot, the material of the electrode or the ground tab will soften, distort, or even oxidize. The metal in a spark plug has a single purpose: to channel the electrical energy through the spark plug. Iridium is far harder than copper and this allows the spark plug manufacturers to create a plug with a sharper ‘tip’ which better focuses the spark around the centre electrode without compromising its service life.

Just put iridium plugs in my K5 and it seems to have cleaned up a very slight light burble of a misfire that I had.

CR9EIX/3521 NGK - Spark Plug Of Ignition IN Iridium, 3 NGK CR9EIX/3521 NGK - Spark Plug Of Ignition IN Iridium, 3

M10 (10 mm) threaded plugs with a gasket show just 10-12nm of torque are needed for aluminium heads. Now compare this to an M14 plug, where we see over double the amount: 25-30nm. Torquing down an M10 plug to 30nm will most definitely cause either distortion to the plug and eventually snap into bits, or the cylinder head thread will strip; not good. Designed specifically for the performance enthusiast Iridium IX offers extreme ignitability, improved throttle response and superior anti fouling. You’ll need this to help you find the location of your spark plugs and how to access them. This may sound simple but often the manual offers up some time-saving tips for your particular model.

Harley Davidson Spark Plug Fitment Chart

Two percent of the people think; three percent of the people think they think; and ninety-five percent of the people would rather die than think."

NGK CR9EIX (3521) - Iridium IX Spark Plug - Opie Oils NGK CR9EIX (3521) - Iridium IX Spark Plug - Opie Oils

so the uber smart engineers calculate that heat transfer path, the average temp for the engine at full throttle and full load, and at idle... proposed engine coolent temp limits and toss in 20% safety margin and then design a plug that will hold self cleaning temps over the widest range of engine RPM, ambient temp, etc. with out ever reaching "burn out" temp and volia' you have a plug for your specific engine. It gets better, the installation guides on the rear of the inner boxes are for an M14 (14mm) diameter threaded spark plug, not M10 (10mm) that CR9EIX features! The fakes terminal caps were finger tight, whereas the genuine caps couldn’t be undone by hand and needed pliers. If you’re going to be doing any sort of work on the bike, treat yourself to a decent set of tools. Most of mine are from the Halfords Advanced range (formerly called Professional). The image of the spark plugs above shows four common conditions that you’ll find your spark plugs in. From left to right the plugs are Normal, Rich, Lean and Very Lean. Full descriptions below.

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Motorcycle spark plugs usually last around 16,000 miles, or at least this is when most manufacturer service schedules recommend you change them. That's typically once every other major service. However if you use Iridium spark plugs they will last a lot longer, usually well over 30,000 miles. Maybe it's time for a little spark plug 101 as it was explained to me by a guy who didn't spout any BS. This is simply one mistake NGK would never make. If you think of how many of these are sold worldwide, you can see where the problem’s heading. The number of damage reports of snapped CR9EIX plugs and damaged engine heads would soar if worldwide customers tightened down M10 spark plugs to M14 specifications. A colossal recall would then pursue as M14 plugs are actually torqued down around twice as much as M10 ones! It’s important to use a torque wrench because under-tightening can cause overheating due to poor heat dissipation and as mentioned, overtightening will cause damage.

CR9EIX (3521) Iridium IX Spark Plugs How to Spot Fake NGK CR9EIX (3521) Iridium IX Spark Plugs

Spark plugs are often called "hot" or cool or anything inbetween... This has NOTHING to do with how hot the fuel burns. It has to do with how hot the spark plug gets. Thread diameters of 10mm, 12mm, and 14mm are the most common. In fact, when it comes to motorcycles, it's rare to find any other sizes in use.NGK is the brand leader in the UK spark plug market and are the world's biggest supplier to many major car manufacturers. Each and every one of their products are designed to meet the most rigorous standards and are the professionals' choice because of their quality and technical excellence. Their plugs can be found in use by teams in F1, WRC and MotoGP. Put simply, NGK genuine spark plugs are the workhorse at the heart of smooth-running engines around the world. A spark plug electrode is litterally at the absolute hottest part of the engine. It is where combustion starts, when compression is the highest it's going to be, and where a lightening bolt (that is a plasma discharge) is purposfully formed. Copper is generally seen as being the best metal to use in terms of conductivity but iridium plugs are seen as premium as they last longer than standard plugs and can be built with smaller tolerances. Iridium spark plugs also have lower voltage requirements, meaning they perform better when starting and idling and some manufacturers also claim they offer a better throttle response. This nifty little tool only costs a few quid and will help you set the correct gap for your spark plug. However, modern plugs are almost all motorcycle-specific fit and so they come ‘pre-gapped’ and you won’t need to touch them. If you’re running a classic bike, you’ll probably need to set your gap and if your bike’s not running right, a gap tool can help you rule out a potential incorrect gap issue. The installation guide error on the fakes may cause even more damage if anyone also ends up using thread compound or copper slip. Using such products renders torque readings inaccurate by at least 20% so they should never be used. Modern plugs feature a special zinc coating so they simply don’t need it. NGK released a tech bulletin about this, which you can read in our other article in the link below: