Behold:

20X view of #4 gap:

20X view of new gap:

20X view of #4 after grit blast:

50X detail of new iridium electrode:

50X detail of old electrode:

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SWEET!Most excellent Hag...T/Y.and...

DAYam.

* Last updated by: Grn14 on 10/16/2015 @ 1:49 PM *

My pleasure, young man!

Don't trust the scale bars in the first four snaps: some nimrod fucked up the calibration factors on my Stemi 2000-C and now the measurements are fooked.

The stated magnification factors are accurate.

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The youngest (mid 30s) of my metallurgists seems to believe that the deposits on the center electrode are sulfur based due to their hue and nodular appearance at the hottest part of the electrode.

I don't have the equipment to test the composition of the deposits; my melt shop lab has spark and ICP spectrometers but they are forbidden from extracurricular activity.

Therefore, we will have to guess at the composition of the deposits. I will say that they are a salt: the combination of a metal with a non-metal.

Since the deposit is heaviest at the large part of the center electrode I will wager on cuprous sulfide.

* Last updated by: hagrid on 10/16/2015 @ 6:44 PM *

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....so don't wait 44k miles before you change your spark plugs ...or they will smell like farts? My new spark plugs make my ninjee feel like it has a fresh new snappy pair of pure white briefs!

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The youngest (mid 30s) of my metallurgists seems to believe that the deposits on the center electrode are sulfur based due to their hue and nodular appearance at the hottest part of the electrode.

Funny how that sulfur base [50x photo] is more like molten balls of aluminum? I say this because they seem to be perfect balls as in hot earth looking are the sphere shapes. Carbon or the contaminants would be on all 4 plugs, but knock happens to 1 chamber starting out, right? I've seen my plugs have those kind of balls, plus, when I looked at the top of the piston, it once had a machined hole to hold in a lathe. Next time I looked, [heard a knock noise under a hack setting], that perfect machined hole looked like a crater with its own aluminum balls welded into that divot.

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I've seen my plugs have those kind of balls, plus, when I looked at the top of the piston, it once had a machined hole to hold in a lathe. Next time I looked, [heard a knock noise under a hack setting], that perfect machined hole looked like a crater with its own aluminum balls welded into that divot.

I think I see those little balls on all of the plugs. The closer views show that the tang that bends over the electrode is concave as though it has eroded more at the center directly above the electrode. This makes sense since there would not be a single path the spark would jump over the life of the plug. As the path of least resistance wore away, a new path wherever the gap was smallest would be established. Over time, these new gaps would occur in a radial fashion burning away the various points that the spark was jumping to from the electrode. I guess that's why we see a uniformly dished out surface on the tang. The center electrode does not look like it is shaped all that much different than the brand new electrode so I don't believe it erodes much but it sure seems to collect globs of something around it.

Britanica:
Cuprous sulfide occurs in the form of black powder or lumps and is found as the mineral chalcocite. Large quantities of the compound are obtained by heating cupric sulfide (CuS) in a stream of hydrogen. Cuprous sulfide is insoluble in water but soluble in ammonium hydroxide and nitric acid. Its applications include use in solar cells, luminous paints, electrodes, and certain varieties of solid lubricants.

So we have balls of something (be they a copper/sulfur compound or just plain steel that melted off the tang) forming on the plug. Hub has seen them stuck on the top of his piston. I guess I don't need to think too hard about why it's important to change spark plugs regularly. There is no way to stop these little balls from forming and bouncing over the cylinder walls a few times but having them clinging precariously to a spark plug and waiting to break off is asking for unnecessary engine wear. The busa is at 10k. Time to change plugs on her too before she goes back into service. Oil, filters, air filters, plugs... it's all the same story, they'll last for ever you want them to but it's no good for the engine.

* Last updated by: Rook on 10/17/2015 @ 8:25 AM *

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Great pics Hag , thanks for posting them up !

Hahaha, Rook said little balls.

I'm at 12K and going to take head and service this down season.
Thanks Hag!
Dave

What is a metallurgists shop doing without a SEM/EDX for composition details??

Ghheeseees lets get professional.

Nice pictures though ....very shiney

* Last updated by: cruderudy on 10/21/2015 @ 5:57 PM *

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Man those are some nasty looking plugs... Not sure if its just the close up but looks like some oil fouling on Cylinder #4 at the least. Also makes me want to head to the garage and check my plugs... :)

It's not conclusive but from the few pis I've seen and sometimes sketchy documentation of what cylinder each of the pugs came from, it seems possible that oil deposits get heavier from left to right. That was pattern I saw with mine. #4 was the worse, #1 did not look too bad even after 44k miles. As far as compression, #4 and #1 were the strongest and both had equal compression..so I don't think the grease buildup had to do with leaky cylinders. I believe if you change the plugs on schedule, you won't see much of a buildup.

Also, my head cover bolts have the same pattern of grease. The left two are clean and the right two are dirtiest. Middles have a little grease but not much.

* Last updated by: Rook on 10/22/2015 @ 4:25 PM *

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Rook!

I sent your plugs back to the enclosed address via UPS yesterday.

Keep your eyes peeled.

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Thanks Hagrid. I'll be watchin. No need to worry about packages growing legs and walking away around here.

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Got 'em. Thanks, man! Hagrid sent me a set of brand new NGK Laser Iridiums! I'm all set to change plugs on schedule or maybe even sooner if the double electrode plugs get too nasty. Thanks for the fascinating pics. That was surely enough. The new plugs are a cool bonus.

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It was only fair.

You did me the favor by submitting samples. It was only right and proper that you receive the same new plugs that served as the control group in your metallographic analysis.

And it couldn't have happened without your generosity.

God willing, I'm going to try to make a longitudinal section of one of your used plugs. If I pull it off I'll fixture it for polishing. THEN we'll get a look at the microstructure of the Cu/iridium interface.

can hardly contain myself!

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I'd love to see the cu/iridium interface and find out what the heck that means. For now we see the side electrode burns or melts away and probably ends up being ingested by the engine or stuck to the top of the piston.

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So, at what mileage would you recommend changing the plugs? Mine has 21,000 mi and she runs better by the day. Plugs never touched.

So, at what mileage would you recommend changing the plugs? Mine has 21,000 mi and she runs better by the day. Plugs never touched.

I forgot: God, I love this bike!

Book says 7500 miles.I think that's a bit extreme.My 1st 14...22K replacement...they still looked just fine.My second 14...24K...they still looked fine.I did not replace those.

7,500mi means basically: 'remain in a high/peak performance tune.' Yes, you can run the plugs for triple that amount, but the sooner you break the threads from the carbon build, the electrolysis bonding the plug threads to the head's threads, the mantra is to remember the chemical reaction vs. current flow. Yes, they coat the plug with a dissimilar metal to deter that reaction, but that is no guarantee down the road.

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Forgot about that!Thanks Hub.Nothin like a little bonding to totally ruin yer day;)

So, at what mileage would you recommend changing the plugs? Mine has 21,000 mi and she runs better by the day. Plugs never touched.

Based on what I see in this thread, I plan to change about every 7500 miles but I doubt it's imperative. It's just a precaution to take before the plugs get too much melted metallic dingle berries on them. I'm sure metal is going to melt off of new plugs too but at least there will not be solid chunks that could break off.

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The new tips show a sharp edge. The rounded tip was repeated 1000's of times is that plasma looking arc. You'd have to find a microscope powerful enough to find the metal burned off that edge if not vaporized into powder. No damage done to the bike in that sense. Think of all the cars with longer installed plugs. Are they damaged from the atoms popping off? No.

A K&N kind of pleated filter would cause more damage down the road. Letting in crap that big would score the cylinders. Plugs do not melt off in that environment. Say det bangs the top of the piston dome so hard as if the ceiling fell, the rings lock up. Say the rpm's are at peak efficiency, rings have no spring, oil gets past, oil burns hotter than gas, now things can begin to melt.

I'm confused as how you see a plug melt?

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