Plug reading - Mixture ring & insulator coloring

I would like to better understand the relationship between the width of the mixture ring and the color of the plug insulator. As I understand it, the mixture ring width is a direct function of jetting, mostly the main and to some extent needle taper. Conversely, the insulator color is mostly affected by the heat range of the plug and operating conditions. Is this right?

As an example, from plug chops I'm getting a mixture ring about 0.030" wide at the bottom of the insulator. The transition from the ring to the insulator is very crisp, less than 0.010" wide. The remainder of the insulator is predominantly white, with some very light coffee colorings. Does this indicate that the jetting is just about right, but the plug is borderline hot for this application?

In reality, I spend very little time pinned WFO in 5th, so I wouldn't think I should go with a cooler plug. Under normal trail riding, when I pull a plug after a ride, the insulator is an even caramel color. So that would indicate the heat range is appropriate for my typical riding conditions.

Just hoping to clarify this distinction.:think:

MikeS - good idea about checking the crown coloration. So far it's running strong & showing no signs of needing a top end, but I'll definitely be looking for that at teardown. Also, I had never thought about checking the ring lands for the same color. Will do that when I pull the pipe off next time for a good cleanup.

As far as wet line jetting, that's a new one on me. Now I've got some more reading & research to do... :laugh:

MikeT - I have read here that some people put in a fresh plug & run a test, then pull it out & cut it open. I guess I'm cheap, cause I just wait until I'm ready to change one out & then do a WFO chop. The last one had 1 enduro and a couple of putt-putt trail rides with my son; maybe 10 hours run time. I did one WFO blast down the sand flats, turned around went the other way about 25 to 30 seconds WFO in 5th, and chopped it. The insulator was completely clean, so if the mixture is right I think you can get a good read on an 'old' plug. I don't think the width of the ring will change with run time, but the ring is definitely darker with more hours. Rich may clarify that... :)

I had to tap a little bit of rear brake, but not much. We've got a wide open sand flat area that's like a beach. It seems to draw quite a bit of power, and does a pretty good job of loading the engine.

But, all for naught now... :( guess I'll have to spring for a new plug to do this right.