Of plug chops and running lean

If anyone remembers the thread I made not too long ago, I had some interesting shenanigans going on with buzzing and general vibration. I did think it was related to poor ignition quality for a while, but I believe I've got it down to the exhaust - likely the collector. Anyways.

While I was problem solving, I realized I hadn't done any plug chops in the over 1,000 miles I rode since getting the carbs in order. All chops were done by simply hitting the kill switch and coasting to a stop.

My first chop was a nice WoT streak, off idle to redline in first - then held it for a few seconds. Bet my neighbors loved that one.
First plug I pulled was rather white, a very dusty brown insulator tip, and most alarming - spots on the insulator. I was now very alarmed that I was getting detonation!
However, the remaining plugs all looked like clones of one another. Mostly white, except with some very light tanning on the very nose of the plug, with dark brown spots on the insulator.
After that, I then did a steady 5k chop. Same story - spots, and barely-there tanning.
Then came the idle test, and no difference on the insulator. There was slightly more soot on the ring, but that's about it.

Now, everything about this says I'm engine-explodingly lean, but it doesn't drive like it. No flat spots, engine is very snappy throughout the RPM range, no hesitation or bogging off idle. Comes down from RPM to idle very smoothly; doesn't hang at all.
Exhaust pipes show no signs of discoloration. Did a ghetto float test by doing hard, jerky stops to try and make the engine hiccup, but it cared not. Ran like nothing was going on.

Where I live all the fuel contains 10% ethanol (soon to be 15%, I think). This, I believe, will give the same signs as running lean due to the oxygen content in the ethanol, as well as its lower energy density compared to gasoline, correct?

As for the spots, I am wondering if perhaps they're due to some sort of contaminant in the fuel? Be it rust that got through or whatever may be.

So far one of my ideas is to partially block off the air intake, see if I can get some color onto the plugs that way - maybe shim my needles. Any of you guys have something to add?

 

You worded your post much better then mine--I have a similar situation where my bike runs great, idles great but is obviously rich. IMO its better be rich then lean because rich will run cooler. I will be following this thread to see whats up.

 

bob did you do a ColorTune?

Try backing all 4 mixture screws out about 1/8 turn and see; sounds like you're right there, but maybe just a tad lean still.

 

According to the various plug charts I've studied,(and so how
I've jugded my cyl fire). all but the first one sounds about right.
There should be a little color on the insulator, the ground strap
can be bare to tan/drk grey, a nice ring of soot around thread
ring, timing mark at the bend in the ground strap, no little spots
(chunks) of alum peppered on the plug.
The range between a good running plug is fairly broad while a
perfect plug is small and rather subjective to the viewer.

 

parts what does the 'timing mark' look like on the bend of the grounding strap?

 

if all is right-You'll see a change in color, or a line, or some
other mark that divides the strap.
Usualy the bottom half will be sooty like the ring on top of the threaded end .
Idealy it will appear right in the middle of the bend showing correct
timing. The closer to the threads the more advanced the timing is.
If your plugs are running very rich it will be lost in soot. If too
lean it will be burnt off.