Would you change this NGK iridium plug?

[TMF]

I'm posting here since ST owners skew older, more experienced and technical. The plugs are from an '07 Kawasaki 650R (water cooled vertical twin) and have 20K miles and 15 years of use. You can see some the brownish buildup. Edges look reasonably sharp though. I figure a high miles rider has seen this during maintenance and reinstalled them for another 20K or more of use but want to make sure.

 

[Slydynbye]

That plug looks OK but, check the air cleaner you might be running a little rich.
Gap looks kind of big but can't tell from here.
Depends how frugal you are.

 

[mortenk]

I would clean it with a steel brush first of all...

 

[jfheath]

I have zero experience of Iridium plugs, and zero experience of having plugs that have been installed for 15 years.

That being said - there is more to a spark plug than just the bit below the compression washer, and my eagle eye spots a bit of something rust coloured up there.

If it was me I'd be thinking.....If I thought that maybe 15 years wasn't an issue, why did I take them out ? The plug doesn't look to be corroded, and it certainly aint running hot. I don't know what the rainbow tinging on the thread indicates.

But I'm a worrier. For the sake of my own peace of mind I'd put a new set in now pleased that I'd had my money's worth rather than wait and have the thought niggling at me for the next few thousand miles.

 

[TMF]

I have zero experience of Iridium plugs, and zero experience of having plugs that have been installed for 15 years.

That being said - there is more to a spark plug than just the bit below the compression washer, and my eagle eye spots a bit of something rust coloured up there.

If it was me I'd be thinking.....If I thought that maybe 15 years wasn't an issue, why did I take them out ? The plug doesn't look to be corroded, and it certainly aint running hot. I don't know what the rainbow tinging on the thread indicates.

But I'm a worrier. For the sake of my own peace of mind I'd put a new set in now pleased that I'd had my money's worth rather than wait and have the thought niggling at me for the next few thousand miles.

The smooth section just below the "nut" part of the plug body is rusted/corroded on one of the plugs. You got me worrying now and just may have cost me a nice IPA 12 pack.

 

[RaYzerman]

At 20K, they have lots of life left, not worn much at all.... I'd clean them up and re-use. Not sure how to interpret the brown colour.... perhaps not hot enough a heat range or maybe a hint of oil consumption/rich mixture going on? Yep, check that air cleaner.

Most bikes have a lost spark system meaning the coils fire every revolution, so 20k in a car is half as much cycling as in a bike. With iridiums, not likely going to see much wear until 50k or so.

 

[CruSTy]

I would go one heat range hotter. Don't take a chance on them rusting in the head, replace them.

 

[Andrew Shadow]

Would you change this NGK iridium plug?

Yes, because the colour indicates that it has been running to rich or to cold, which can cause the to rich indication as well. Cleaning spark plugs has not been recommended for years because it can damage the special coatings that have been applied to spark plugs for many years now. Spark plugs are cheap. I would replace them, but not with iridium unless the price differential was inconsequential. There is nothing wrong with the recommended standard NGK or Denso spark plug of the correct heat range.

Are they the correct heat range for the application? They should not be that dark in colour if they are.
Below is what a standard spark plug from my ST1300 looked like after having been installed for 98,000 KM, or 60,000 miles.

 

[TMF]

Thanks for all the replies. Many noted the bike may be rich or the plugs too dark. The actual plug as compared to the photo is a light tan, not a darker brown and is burning well. Considering everything and the hassle of getting to the plugs, I ordered a new set primarily because of exterior corrosion on the metal parts of the plugs (Connecticut bike). I've been putting iridiums into all my bikes for some years now and haven't accumulated enough miles to change one on any bike. It's good to know that even with 20K miles a set is halfway or less from needing replacement.

 

[Andrew Shadow]

It's good to know that even with 20K miles a set is halfway or less from needing replacement.

No spark plug installed in a properly running engine needs to be replaced at 40,000 miles despite the Honda recommendations, let alone an iridium plug which is supposed to offer even longer replacement intervals.

 

[Upt' North]

DON'T wire brush them, just my view.
Upt'North.

 

[SMSW]

There have been discussions about counterfeit Iridium plugs. You might read a few of them - do a search for "counterfeit iridium", click on Search in the blue band atop this page. A number of threads pop up.

 

[TMF]

No spark plug installed in a properly running engine needs to be replaced at 40,000 miles despite the Honda recommendations, let alone an iridium plug which is supposed to offer even longer replacement intervals.

The exception might be the 1987 Honda CBR600 Hurricane I owned for 10 years. Every fall I'd do maintenance including taking the conventional plugs out and checking the wear and gap. They would go back in despite Honda's recommendation to change them every 4K miles. Every spring I'd push the bike up and down the hill in front of my house 2 or 3 times until it would light off on a bump start. During the season it was easy starting as long as you let no more than 2 or 3 weeks went by. I always figured it was a lean idle circuit. Eventually I changed plugs. That spring it started easily and thereafter the plug change interval became no more than 4K miles.

 

[Oldbikefixr]

I have had several bikes that would have embarrassing plug failures between tuneups on point systems, many under 2000 miles. I was discussing this with another restorer back in the mid 90's (my 1978 GL1000's) who told me that not all condensers were well made and cheaply made ones broke down quickly. So, I began replacing condensers at every tuneup, something I did only at the initial rebuild....no more problems with early plug failures.
Recent history confirms his opinion for the most part, no further problems with the GL's, none with either electronic systems on the ST1100 or ST1300.

 

[rwthomas1]

Iridium plugs can last 100K. Clean them gently with an old toothbrush and reinstall. I like a little antiseize on the threads, but others willl tell you not to. If the engine is running well, and performance is good, mpgs are normal, there is little to gain in swapping them.

 

[TMF]

The latest is that NGK promises to examine my photo for plug wear and buildup then offer an opinion as to whether it remains in service. We'll see. Customer service has huge degrees of variability.

Update: NGK says the plugs are reddish indicating high levels of octane booster that has left deposits that will eventually need cleaning. I respond the plugs are light tan. They come back saying in that case they look good and reinstall.

 

[TMF]

I have had several bikes that would have embarrassing plug failures between tuneups on point systems, many under 2000 miles. I was discussing this with another restorer back in the mid 90's (my 1978 GL1000's) who told me that not all condensers were well made and cheaply made ones broke down quickly. So, I began replacing condensers at every tuneup, something I did only at the initial rebuild....no more problems with early plug failures.
Recent history confirms his opinion for the most part, no further problems with the GL's, none with either electronic systems on the ST1100 or ST1300.

Good to know as I'm actively restoring a '75 Wing with 30K miles on the clock. By the way, the '87 CBR600 had an electronic ignition but seemingly weak in some way if Honda called for 4K plug change intervals.