Lean ?!

    Hello guys, I was trying to figure out why I have black plugs and 1 « good » when my Afr numbers look like a bit lean at cruising… The bike left the dyno last summer. The guys tried everything .. at 3000-4000rpm the bike bug so much, after is going crazy !!!! Theres is a Lean bug or not ?! Thank youu

The plug on the right is pretty much spot on. The plug on the left is either way to rich or has a weak spark or low compression or worn valve oil seals or the plug heat rating is too low or the enricher seals are letting by or the bowl fuel level is too high or crappy ebay jets fitted or a combination of some or all of the above. 
What diagnosis has been done. Just messing with carb settings isn't diagnosis. You need to be systematic in the approach. 

Vm28ss 26mm float height, 150 psi on all 4 cylinders, brand new rebuilt, 3 black plug and one like you see !!  I will replace choke plunger in 2 weeks. Maybe its the problem ?!

Tuner put 102.5 on 1-4 cylinders and 105 2-3 cylinders, pods filters with air corrector jet, 15 pilot jet(he tried 17.5 pilot).. stock needle

What model bike are the carbs fitted too? 

If he didn't use genuine mikuni jets all bets are off. That would be he first place I'd be looking. Ebay and 99% of aftermarket jet kits are just total junk and cause more issues than they solve. I'd want to prove to myself the jets are genuine. Mikuni jets have a box in box logo stamped onto them.
 

Next thing to check is the physical fuel bowl fuel level. Doing an upside down float height measurement is largely irrelevant other that to get a base setting. It's the fuel level in the bowl that matters and that can only be done by testing them using the wet method. 

What plugs are fitted? If you have resistor plugs and resistor plug caps fitted that'll cause a weak spark which will cause the symptoms showing. 

There are mikuni jets, b8es spark plug’s and coil resistance are good!! 3 black one with one good. Weird 

I might ask on the 3 plugs that are dark, is it oily or sooty? Further, which plug looks OK, 1,2,3, or 4?

1-2-3 sooty yes and the last one (right) number 4, pretty good!! Dyno numbers are great but cruising feeling is bad

AFR between 3,500 and 4,500 looks lean to me. An air cooled carb motor want's to be around 12:1 - 13:1 (lambda 1 at 14.7:1 is too lean for an air cooled motor and will run hot)

Do you have an idea why the tuner have not been able to correct that range ?!

wrote:

Do you have an idea why the tuner have not been able to correct that range ?!

These are the compromises you have to make with carbs when compared to FI - this is the point where you move onto the needles and "main" jet, any changes to the jet size will cause a richening all the way from this point to full throttle and the AFR looks good above 5000. Raising the needle may help but will again richen the mixture from this point through to approx 75% throttle. Only my opinion but I think your tuner has pretty much optimised the AFR across the range which means a compromise at this point. Possibly going up a size on the pilots may help to some degree

He told me when he try to play with needle, he was not happy with the flat spot !!! Choke plunger maybe?!