Spark plug only half colored

[que_006]

Let me start by saying I've probably read close to 300 posts and website information regarding spark plug reading but really didn't find much regarding my question. When I pull my plugs I notice that only halfway around the base ring and porcelain is colored. From the limited info I've gathered online it could be because one side is on the intake side and the other on the exhaust side? Also, I realize that in order to get a proper reading I need to cut out the threaded area to see the base of the insulator and I have, just not in these pics. I've attached some pictures to clarify if anyone has any questions. Let me know if anything else stands out to you. Thanks in advance. 17181090311718109030

[MtnEX]

Right...

Me, I see nothing crazy. Looks fine.

I can however tell you what causes this... the primary factor involved is head flow and cooling.

The colored side is facing your intake valves side and the uncolored is facing the exhaust. The cooling effect on the intake side will allow for deposits to form faster, while the heat from the exhaust side will keep them burnt off longer.

I don't know what throttle range that plug was ran in last, nor for how long the plug has been ran overall. But if it runs good, and feels good, and the plug doesn't have much time on it, I would leave the jetting alone.

[que_006]

Thanks for the answer. It runs great except for the huge miss I get when blipping the throttle from really low rpm's to full throttle. Going to take the carb off today and check the accelerator pump and a few other things.

[Zakradu398]

Go to a 42 pilot while its open if it's not excessively hot (90+)

[que_006]

Just put an order in for a 42 pilot but I found out the problem with the bog off idle. Turns out I put the spring on the wrong side of the accelerator pump diaphragm last time I took the accelerator pump cover off. :uhoh:

[on the rocks]

when plugs are half colored like that it is usually a valve seal leaking on the plug causing a black build up on the leaking side from the burnt oil. doubt the plug reading had anything to do with your running concern.

[slightlybent47]

Could it possibly be that the geometry in the combustion chamber be a little off causing an uneven burn in the chamber. Causing a little more heat on one side of the head.
If it runs good and you are not have a over heating issue, I'd try running it that way a little longer and see if the plug gets more even color after more run time.
Can say if any of that will help, but might be worth a try.
How long did you run it with that plug? and how hard did you run it?

[slightlybent47]

Use a Sharpie and even it out. lol

[que_006]

Well I tried the sharpie idea and it seemed to fix the problem. Hahaha! I think I probably had 15 or so hours of run time on that plug at least. I don't know, I guess I won't worry about it until I notice a problem with how the machine runs and just check the plug periodically for reference. Thanks

[slightlybent47]

Try a different plug. The threads and the lead may not always line up the same on all plugs. Putting the lead in a different spot in the cylinder.
just a guess, Stranger things have happened.

[slightlybent47]

If it runs good and is not lean or rich, run it.