1996 Fatboy @ 5000 ft. Altitude
Keihin carb w/ Arlen Ness Stage 1 Big Sucker
Running 185/46 jets
1 1/2 turns on mixture screw

too Lean?

 

Trying to tune via reading plugs is tough to do. The plug looks okay to me. Evos like to run a touch lean anyway... you probably have the “lean gurgle” exhaust note on de-acceleration, nothing wrong with that, if it’s popping on de-acceleration, then maybe it’s too lean.
You might want to coat those threads with a bit of anti-seize.

 

I'm gonna guess that is from the front cylinder. Also gonna guess the rear cylinder is slightly darker in color. If so looks just like mine (48/190) with a well ventilated intake and exhaust.

How does in run? No ping? Not to hot? Leave it alone.

As long as no ping, no pepper looking material (black is carbon, grey is aluminum), no cracking or shine to porcelain, your good. Your heat range is touch hot, but hard to tell with the antiseize on the threads. If replacing plugs, maybe one step colder. What is your timing set at? Factory curve or aftermarket?

Gogobeck just described how my bike sounds on de-acceleration, as if he has heard my bike before...

I had the same concerns as you and one of the regulars here (T150vej with way more experience/knowledge than I) pretty much told me the same thing.

Get a wideband if you really want to dial it in. It's on my xmas "want list".

 

In general, a leaner mixture makes more power right up until it doesn't. Is the bike running well?

 

No popping on deceleration. Always use anti seize. Seems to run okay, feels a little rougher but got better throttle response.

 

Hey Yankee Dog, good to hear from you again brother. No popping on deceleration. Always use anti seize. Seems to run okay, feels a little rougher than before but got better throttle response. Might be feeling the power more. I thought of maybe taking the mixture out another 1/4 turn. Keeping an eye on the plugs for any tell-tale signs.
Running RN12YC plugs.

Just found a local bike shop with old school mechanic. He’s got a ‘97 Heritage getting 50 mpg here at altitude. I will be taking this in to him to get fine tuned. He’s been really cool about sharing knowledge.

you get a hankerin’ to head to Az, give me a holler.

 

Dr. Hess,

bike seems to run ok. I feel more response to the throttle.

 

Here is another look at the front plug.

 

Plug looks good I wouldn't say it's lean at all but it seems like you might be having too much timing in there... You get any pinging at all, light throttle tip in say 2500 to 3000 RPM 4th or 5th gear?

 

98hotrodfaboy...................no ping.