Spark plug question

[lilgman]

I've been reading posts on this forum about all the great mods that people do to these bikes. One of the most common is re-jetting the carb. I'm happy enough with the way the bike runs so far, but I don't want it to run too lean. Today I adjusted valve lash on it. (A Big Boy 250--basically a Hawk but with a balanced motor), so had the plug out. It looks like this.



Am I correct that it's not running lean? Maybe even a little rich? Or too cold? The plug is a NGK D8EA. I'm not seeing that as "recommended" on this forum. Is there anything to be gained by changing to DR8EIX or NGK 2202?

The carb is stock but I don't know what jets are in it. Our elevation is 1600 meters or 5250 feet above sea level. This was not after full throttle. Lately my riding has been on foot paths, so mostly 1st and 2nd gear light loads, low to medium rpm. I haven't run the bike hard much, but I have no complaints. The throttle is responsive; no falter. It seems sluggish at high rpm, but from what I'm reading, that's par for the course with these engines at least until they have a few more miles on them.

Thanks in advance for advice!

[Wild Dog]

What's the color of the tip?

This a chart from NGK




There are others that gives more example of rich and lean but this one is basic and clear.

[Megadan]

I would definitely say it is on the rich side. You being over 5000ft in altitude means that a lot of the jetting advice found here likely won't apply to you as many of us live at or below 1000ft. At your elevation the factory jetting is probably close to correct, or even a little rich.

Since you stated a lot of your recent riding had been at low speed and light throttle, I would recommend adjusting the idle mixture and/or maybe stepping down to the next smallest pilot jet. I.E. if it has a 40 installed try a 38.