Spark Plug Querry?

I've been using Denso Iridium Spark Plugs IXU27 for a good 5000 miles I reckon. I'm happy wsith the extra performance the Iridium give. I'm preparing to service my Buell myself this time, not sure if I should change the plugs at this stage? The up side is that it's done together.

Anyway my confusion is I don't know which Denso plug to go for. If I search on Densos worldwide site my 2009 XB12ss is not listed. If I search on eBay I have one choice but no Denso number is listed so I don't know what they will send me. Some people seem to use IXU24 according to what I've seen on this forum and on the internet and on Spark-Plugs.co.uk they list my bike needing IXU27. Talk about confusing!!

Any ideas?

i have been using ngk dcpr9eix iridium tipped in buells for 11 years now with great success. below is your cross reference for denso.

http://www.globaldenso.com/en/products/aftermarket/plug/cross_reference/1037_8.html

From what I can see the DCPR9EIX is the same as the Denso IXU27, So I guess I have the right ones in already. I must admit I don't understand the colder vs hotter plug. I'm guessing in the NGK range, 8 is colder than 9? Denso IXU24 is colder than IXU27? The hotter the plug the hotter the cylinder?

Basically, very simplictically, on a 'hot' plug, the porcelain part of the plug is 'smaller' or thinner, so it stays 'hotter'. This will help on an engine at low rpm, light loads, start and stop, etc., to keep it 'clean' so as not to 'foul' and cause a misfire. There a LOT of things that come into play here, but I say this is a simple explanation to help you grasp it. A colder plug is just the opposite...a 'fatter' porcelain carries the heat away, thus it's considered a 'colder' plug. Many times, high compression, high rpm, high load REQUIRE this...bad things happen running too hot a plug on a race/performance engine. It can actually stay hot enough to light off the next round of air-fuel charge before the ignition spark does, resulting in just that...pre-ignition. The results are basically the same as detonation....broken ring lands, etc. as well as some melted parts can happen. But....long story short...use what is reccomended for your bike. I THINK they spec the Lightning as a hotter plug, thinking most guys do a lot of 'town' riding etc., whereas the Firebolts are a colder plug by one step, with the assumption those guys will be in the throttle harder and longer. The engines are identical, so that's the only reason I can see for the different spec. I would say it comes down to your riding style. If you're doing a lot of short runs, start and stop, and not really getting out there and getting some heat in it, run the hotter plug. If you're going out there and running it hard or doing a lot of hiway stuff and not starting/stoping all the time, run the cooler plug. But I would NOT exceed the ranges of the spec'd plugs of either machine for an internally stock XB engine.

I'm guessing in the NGK range, 8 is colder than 9?

Click to expand...

no. in the ngk world the lower the # the hotter the plug.

If i'm not mistaken, ONLY the NGK world, correct?

Thanks for that. My style of riding is not town start/stops but non stop hard on acceleration riding along A + B roads mainly. Not much highways as I tend to avoid them but a lot of overtaking and riding hard in the twisties. I aim for quick acceleration always. My most frequent and shortest ride tends to be about an hour long. I only ride for pleasure!

I've been impressed with the Denso plugs, put them in my RD350R, my then RD500, Buell XB12. On my GS adventurer I couldn't get the Densos at the time so the garage fitting NGK Iridium's instead. Didn't seem to make much difference, not sure if that was the bike or the choice of plugs but the faster throttle response wasn't as noticeable on my GS with NGK vs my others bikes with Denso's

Lastly, how do you quote someone elses post in yours? I can't see how I can do it, theres no option to quote anywhere?

With that said, I would get the plug they call for, for a FIREBOLT. (as I'd explaineded earlier). Choose a plug BRAND that YOU like.....everyone has their own opinion on plugs....honestly, they all work...some maybe better than others. I have NGK's in mine for 30K miles now. But....I've run regular old Champions (Which IS the OE plug in these), for a ton of miles as well. The ONLY way you'll honestly FEEL any difference in any plug, is if the plugs that were in were just plain shot. We did all kinds of EXTENSIVE dyno testing with different plugs and wires. These claims they make are just a bunch of marketing. Sure...you take a pair of plugs out that have 40K miles on them and replace them with ANY plug, it should run better! Lol!