Marco, that helps immensely, thank you.

All your observations about my bike were correct.

But in addition to the high temp rear cylinder head (which has since come down from 350 to 318 after removing my lower fairings. I also took away 6* of timing but that didnt seem to make a huge difference, but I totally get your point about the importance and impact of excessively advanced / retarded timing), my first priority was validating / correcting the mixture. The map I had from my builder was Advanced, with different tunes front and rear. The map I got from DynoJet was Basic, and I promoted it to advanced. When I ran it, the consistent AFR difference front to rear is what prompted my most recent line of inquiry. I needed to know if that difference implied a problem I should correct before adjusting my Advanced DynoJet map for proper a/f mixture targets.

I can now stop worrying about that difference and get down to the business of adjusting this per ypur suggestion: 13.5 across the board and adjust from there.

Thanks to all of you for not throwing your hands in the air and walking away from this in frustration. If I could, I'd throw a big frickin party for you all when this is done, with kegs and sodas and strippers and donkeys and midgets and monkeys, and maybe even preachers in drag just for the hell of it. And I'd even pay bail after for the less fortunate

(And hopefully *that* didnt make anyone want to quit helping! Lol)

 

Put tape around throttle grip. Put tape on switch housing next to throttle. Mark a line on the switch housing tape. Mark corresponding lines/throttle positions on the grip (use PC intervals 5-10-15 etc) Then you can ride at various RPM and TP intersections and make note of the AFR and adjust. You will also get a feel for what areas equal heavier loads.

Idle 13.8-14.2
Cruise 13.8-14
WOT - 12.5-12.7

Oh yeah - put it on a dyno...

 

i haven't had to do the tape thing since i learned how to do mikuni's back in the day, but it will work, and you can go even one step further with it, tape up the grip like Ed showed, open the pc3 software and power up the pc3, then use the throttle position data from the software and mark your grip/tape setup and compare to the screen to get a very accurate measure.
m

 

Good tips.

My Innovate Motorsports data logging rig captures mixture, RPM & throttle position but I'm going to do this anyway for real-time feedback to inform the "seat of the pants" component of the tune.

I'm trying to concoct a way to connect the temp sensor to the logger so I can see how mixture and timing adjustments effect heat.

 

can you program in the resistance values from the stock sensor and tap that harness?
m

 

Remember that you are only reading temp from the front cylinder head area on a TwinCam. So you are in trouble if you want to know what the rear is doing unless you add a sensor to that head.

 

Thanks Steve. Yes, I'm aware. Logging front CHT will be for trend analysis rather than to aid in diagnosing the issue I've had with rear CHT.

Interesting thought tho: I think I have room on my data logging rig for two more inputs, one of which I'll use for the factory engine temp sensor. If my rear head is also drilled & tapped for a sensor, I could add another one there solely for the purpose of logging data with no connection to the ECM, giving me both front & rear CHTs. But... I didn't see a hole for it when I took a quick look.

 

the whole engine is inter-twined.
if you ever work on engines like big natural gas lean burn cat, cooper-bessemer and delaval, you will quickly see how changing ONE cylinder will effect all others, holds true for all multi-cyl engines. electronic feed back can only go so far. a look into the short/long term fuel trims will tell all.

 

 

once again, does not matter if you are pouring the fuel in with a 5 gallon bucket, makes NO diff open or closed! on a multi-cly engine, they all inter-twine, one effects the others and getting perfect balance is extremely hard, keeping the diff to 10% or less is the goal.