NGK(3521) CR9EIX Iridium IX Spark Plug, Pack of 1

Received high quality NGK iridium plugs as expected. Works perfect for my Yamaha FZ09 and she runs smooth as butter.Note: just use pliers to gently unscrew the metal top. You install without them for FZ09.

Very good

I went to these plugs for my FJR1300 after dealing with a pre-detonation I was attempting to resolve. The FJR calls for a one step hotter plug in the standard, copper plug configuration. After much research, found out that it's good practice to go down one heat range in plugs when substituting to an iridium from copper - especially when dealing with extreme hot weather conditions ( last time I rode it was 111F). Iridium plugs burn a bit hotter due to their construction (small tip design and low heat dissipation properties). In extreme heat iridium plugs can act like glow plugs, causing pre-detonation, which is what I was experiencing. After going to this one step cooler plug, performance was back to normal.

I had purchased my first set of these last year (2015) as a spare set of plugs to keep in my Yamaha AR210 twin engine jet boat. The OEM NGK plugs are known to have short life span due to the high revving of the engines in these boats. This is the first season I have them Installed in the boat and I am certainly not dissapointed. The engines start better and perform better. I will be using these plugs going forward.

Spark plug... good job.

Installed these (CR9EIX) in my Suzuki Katana 750 and what a difference from the stock plugs which were CR9EK. CR9EK are what they call dual electrodes which run about $10 a plug. Then I read about the CR9EIX plugs and found these on Amazon for about $8 a piece. By nature the Katana is a cold runnning bike but these plugs made warmups faster and the bike runs smoother. Most would say that the ignition system can't support these plugs. I say check with the NGK website or the dealer microfiche. I got 19k out of the stock plugs and NGK says I should get double that with these. And as you know, a Sport Touring bike has many panels to remove and a gas tank before you can see the plug wires. These were worth the time and effort to install rather than the stock plugs.[...]

I replaced my original plugs in my '03 Triumph Speed Triple with these after reading reviews on the Triumph blogs. Instillation was easy and the size was perfect. I also changed the oil on the bike and used a K&N filter (see my other review). The bike starts up immediately, idles nicely, and the extra torque has now returned. Its like riding a brand new bike. I am very happy that I search the internet and found these. If you search the web, you will see that others have paid a much higher price for the same item. The deal on Amazon can't be beat.

July 20, 2015, What can I say.. if you're expecting 10 hp boost it's not gonna happen here. they do work great in my 2004 r1 just watch the top when ya put them in.. it's easy to take them out of gap when installing.Update.. 6/30/18just changed out these plugs and air filter. I was getting a little bit of a miss and figured it was time. Plugs look great, but I do have a couple of things to note.. yes as everyone has stated the top part of the spark plug does unscrew to fit on the r1.. and there is no gapping on these spark plugs. please don't attempt it, you'll just waste your money from breaking them.