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I have a 1999 Suzuki GSF600S that's due for spark plug replacement. The manual calls for NGK CR9EK plugs which are multi-ground plugs. The NGK website also says that the NGK CR9EIX Iridium plugs can be used on my bike. My questions: Are iridium plugs worth the extra 10 dollars for a set of 4 (I'm no MotoGP racer) and does it matter that the iridium plugs are not multi-ground ( no adverse effects ) ??

Thanks for any help!!

bandit600 wrote:I have a 1999 Suzuki GSF600S that's due for spark plug replacement. The manual calls for NGK CR9EK plugs which are multi-ground plugs. The NGK website also says that the NGK CR9EIX Iridium plugs can be used on my bike. My questions: Are iridium plugs worth the extra 10 dollars for a set of 4 (I'm no MotoGP racer) and does it matter that the iridium plugs are not multi-ground ( no adverse effects ) ??

Thanks for any help!!

I went from standard copper plugs to platinum plugs on my bike and noticed that it became easier to start and ran a bit smoother. Plus the obvious increase in plug life with platinum plugs.

A lot of guys I know saw similar benefits switching up from the NGK OEM copper plug to the NGK iridium plug. At the very least, the plugs will last many times as long as the standard ones. At the best, you'll get a noticeable increase in performance.

For as rarely as plugs need to get replaced, $10 is nothing. I'd go for it.

Check out this guy who did exactly that:

http://www.sportbikes.net/forums/showth ... p?t=301788

"So far I've only taken a short run with the new Iridium plugs, but the bike definately feels smoother. Some people have reported an increase in fuel economy as well, and I'll be keeping an eye on that on upcoming rides. If there was any more power, you wouldn't notice, but it definately is smoother running."

Multi-electrode plugs don't help performance any. You still only get one spark per firing event, unless you are running a multi-strike ignition system. Your factory ignition system is not multi-strike. All it does is allow another path for the spark to follow if one path carbon's up or the gap increases too much.

Iridium and other rare metal electrode plugs work fine, they work best with higher output ignitions. Older point styles may be too weak to get and keep the electrode hot enough to remain clean of carbon, and can foul. But your bike should be O.K. on them.

From what I understand of the ignition system the only real benefit that you're going to see from changing to them on a stock street bike is that the electrode itself will last longer without wearing down. Anything else is just a, "oh I think it feels better," kind of thing.

I agree with Sev about any performance gains from a spark plug alone. Provided both plugs are operating correctly, your plug design would have to be pretty messed up to affect combustion negatively.

The S.A.E. did a study in the 70's and found a spark plug can missfire up to 20% of the time before it becomes noticeable to race drivers. They used the big names in Indy car and Nascar of the day for these subjective tests, FWIW. I find that number a little high, but I still believe a plug can fire inconsistently and have no effect, or very little on how the engine runs. I've seen it, with diagnostic equipment attached, and also how a change to new plugs reads on the diagnostics and how it feels.

But if your plugs are missfiring, let's say, 10% of the time.... coffchampioncoff.... and you replace them with a plug that claims performance gains, you will possibly feel a slight improvement. So you are now convinced that your new 13 prong, bone china, plutonium-tipped plugs are the hot ticket.

But if you ask around, everyone has an opinion about spark plugs, what works and what doesn't, what the best construction, materials are..... I think going with a good quality, standard design plug is the best way to go for most engines. Fancy plugs won't hurt, but they won't work any better than regular decent plugs. Your mileage may vary.....

So those plugs are more for posturing and bragging rights, rather than any meaningful performance gain then?

Unless called for by high performance engines, yes it's all posturing and posing.
That said a lot of high performance engines do require a high performance iridium/platinum spark plug.
And if you're running decent compression with some boost a multi-point spark plug can come in handy. Otherwise on most any stock street engine don't worry about it.

Hey, I think I just bought the same iridium sparks from AutoZone and they sold me a 5/8 inch socket to get them changed out with. It fits the new ones but I'm having the hardest time getting the old ones out. Do I need a 16 mm or should I keep trying with the 5/8? Thanks a bundle.

Just replace your plugs at the manufacturers recommended interval and you will be good. No need to use expensive ones.

I wanna know much about Iridium Spark Plugs too.