Iridium alloy has extremely high melting point, perfect for todays high-tech, high-performance engines 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.

CR9EIX (3521) | Sparkplugs Ltd NGK Iridium Spark plug CR9EIX (3521) | Sparkplugs Ltd

If you’re servicing your Aprilia, now’s the chance to upgrade your spark plugs to longer-lasting Iridium ones that will save you money in the long run. PLEASE NOTE – This article was written a few years ago so not all information provided may be accurate. For example, on some part numbers, NGK now uses Laser Etching instead of stamping, so the font information may not be accurate. Another Sparking Discovery Bill I can get you a set of Denso plugs,but I don't think they are anything special... The thing is the cheapest I can find is 44 € ( 11 € each),which is really a normal price here in Greece,since the CR9EIA retail at 15 € each... 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 machined quality of the genuine plug is far superior with a much smoother appearance from base to thread. If you’ve not changed your plugs before, give yourself a couple of hours to complete the task. Here are the essentials you need for smooth re-plugging:

Aprilia Spark Plug Fitment Chart - Biker Rated Aprilia Spark Plug Fitment Chart - Biker Rated

As stated above, the illustrations on the rear show installation procedures for an M14 threaded spark plug. Unfortunately for Mr Counterfeit, CR9EIX spark plugs have an M10 sized thread! This fatal error has already fulfilled our suspicions that they’re indeed fake, and we haven’t even seen the plugs yet! Still not convinced these are fake plugs? One of the best parts of this whole investigation is that we of course found out the fake plugs don’t feature any IRIDIUM tipped centre electrode at all, it’s all LIES.

NGK Iridium Motorbike Spark Plug CR9EIX9

I think, don't quote me, but I think the difference between the CR9EIX and the CR9EIA-9 is dual electrodes. All three are .4 mm iridium center electrode, 10 mm thread diameter, 19 mm reach, 16 mm hex, .9 mm gap, and 5 kΩ resistor. 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.

Spark Plug NGK Iridium CR9EIX vs CR9EIA-9 - Kawasaki ZX-10R Forum Spark Plug NGK Iridium CR9EIX vs CR9EIA-9 - Kawasaki ZX-10R Forum

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. The fakes terminal cap shape is pretty accurate, however cast mold lines are visible, unlike the genuine plug.

Motorcycle Spark Plug FAQ

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 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.