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Bad plugs or too lean?

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Just getting the bike ready for the Yosemite rally and needed a valve cover gasket. Pulled the tank and then the plugs. What happened? #2 and #4 plugs electrode almost disappeared into the ceramic. I've seen lean conditions where the electrode looked melted and pitted. This is perfectly flat and was still firing. (even though the gap was WAY off) The color on the plugs is perfect. Could I have gotten some bad plugs?
 
The first two pics show the good plugs and the second two the bad.
Weird!
 
Honestly the plugs dont look horrid at all. Maybe a touch on the ashy side, but bad enough to cause any damage at all. Prolly bad plugs, but check that maybe those two pipes hotter than the other?
Might need to richen up on two cylinders.
 
Wow! Pretty scary looking. Was the engine running hot? Side electrode looks pretty normal; not melted. Usually if the engine is running lean there are some symptoms. Maybe put in some new plugs and go do some plug chops?
 
The color on the plugs is perfect. Even the bad plugs. I didn't even know something was wrong. Instant start and plenty of power. Can't wait till good plugs are installed.
Bought them all together. Maybe bad? Never had a bad NGK before.
 
How old are the plugs? Where they all replaced at the same time?? Since you are getting ready to take a trip, I'd replace all four of them with some fresh ones. If the problem returns, epecially on the same cylinders I would think that it's not the plugs and something else must be going on.
 
They might have a couple of thousand miles on them. All bought and installed at the same time and two are still good.
 
That's not a B8ES, but can't read the whole thing.
Is it the right heat range?

Must have gotten too hot, very strange.

Got a good close up?

Chances of defective plugs seems slight, especially two of them in adjacent cylinders. One in a million.
It's something else.

My guess would be too lean at full throttle.
Just a guess though.
 
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tkent02 said:
That's not a B8ES, but can't read the whole thing.
Is it the right heat range?

Must have gotten too hot, very strange.

Got a good close up?

Chances of defective plugs seems slight, especially two of them in adjacent cylinders. One in a million.
It's something else.

My guess would be too lean at full throttle.
Just a guess though.
Click to expand...
I noticed when it got hot here in Bako that it ran better when cold than fully warmed up so I threw some 137.5s in. I was running with 140s. I should just toss those back in to be safe.
 
Maybe check & verify ign timing, too lean
 
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I really can't tell much from your signature. What's the compression ratio of the engine? What sort of fuel are you using? What sort of ignition are you using. Where is the timing set? What sort of cranking pressure are you running?

I have wrote about this at least 5 times now on this site but will repeat it once more. I use the heat line. I could care less what the color of a plug looks like. Many reasons, search..

I can't tell anything from your pictures. Sure they melted, seen it, done it, don't want to do it again. Friends nitous solenoid (fuel side) failed about a month ago and we got to see some that looked worse than yours. I have done all sorts of damage in these conditions including melting pistons, fuseing the wrist pins into the rods and even pushing out a copper gasket last year like it was putty. That was a sad day....

Five simple rules.

1. I use D9EA set at 0.024" but I have that flame throwing ignition.
2. I use high grade fuels except for those long idle engine break-ins.
3. I use lots and lots of fuel. I keep the heat line to less than 1 1/2 threads. Sometimes under a thread. I would rather give up power than melt.
4. I never add more timing than the motor can handle. I would rather give up power than melt.
5. Maybe most important, I never crank up a motor all it once. I take small steps, checking the plugs, etc as I go. This is the cheapest way to adjust things...

Hope this gives you something to ponder anyway.

Good luck.
 
10.25:1 compression ratio
Stock ignition
Hi-test Chevron
Heat range is 3-3.5 threads.

Thanks for your input.
 
chef1366 said:
10.25:1 compression ratio
Stock ignition
Hi-test Chevron
Heat range is 3-3.5 threads.

Thanks for your input.
Click to expand...

I agree with Lecroy. At 10.25-1 you are running too hot a plug. The fact that you haven't previously had plug problems probably means that you were running too rich in the past and in lower ambient temperatures.

What octane rating is your Hi-test Chevron? You should be running at least 95 octane.
You are running 1150 spec Wiseco Pistons and 1150 carbs. Are you jetting your #2 & 3 pots richer on the mains as the 1150's do? Their stock mains with the airbox fitted are #1 &4 @120 and #2&3 @ 122.5.
Try a new set of D9EA plugs, and go back to 140 mains. And don't believe all the cheap ass's who say how well their GS's run on low octane fuels. They're often not hammering their engines in as extreme conditions as you do!
 
Again, where is the timing set and whats the cranking pressure? This will give me an idea of how you have the cam and deck height set. After your little melt, it would be interesting to know the before and after numbers for cranking pressure. Melted parts are never good.

That low a CR is no problem. I think you could run it on almost anything and be good to go (as long as the fuel is set right).

My own experience, 3.5 threads is just asking for it. If you start to see 2 threads, you better be adding more fuel! If the stock ignition is in good working order, your should be fine at this CR. Add more fuel and go with a colder plug. This time just try some 1/8 mile wide open runs and watch the heat line. Best to add a lot more fuel then dial it back. Safer.

I would pull it back apart and recheck the pins (I hate Wiesco pins), crank, pistons (look in the ring landings). Any damage to the crank, send it off. But, this is me. If you do decide to just change the plugs and run it and there is damage, you will get a new lesson on how to lighten your wallet. Your bike, your call.

Good luck.
 
49er said:
And don't believe all the cheap ass's who say how well their GS's run on low octane fuels.
Click to expand...
They even suck with 87 octane in stock form, 37 degrees timing all in @ 2500 rpm what were they thinking?, 4k give it some moderate throttle and rattle, rattle, rattle.... ('82 gs850g)
 
Brought the plugs to the dragstrip to show Kris V. He said he's never seen a plug melt while the end electrode stayed perfectly cymmetrical and flat. If it had melted it would be rounded off and the ceramic would be melted.
Bad plugs in my opinion.
Still though I put back in the 140s and went with a D9EA plug. Runs great!

Stock ignition timed stock
The intake and exhaust cams are both set to 110 degrees.
 
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