1981-A3 restauration

I agree with KB. There should be no need to change jetting on an otherwise stock engine with a DG. I've rebuilt many sets of carbs, installing, adjusting and test riding them on my stock/DG headered bike prior to delivery. My custom air intake/K&N filter does not have any adverse effect on tuning and I'm using the listed NGK "6" R plug.
I tried leaning-out the top end some time ago to see if fuel economy would increase. I moved the clip UP 1 slot from #3. At Hwy speed the engine surged and required constant throttle input . In my case, dropping the needles one groove made the top-end, too lean. Went Back to #3 (center groove) and all was good again so I wasn't interested in going the other way by 1 groove but it's safe to say that the plugs would have indicated the extra fuel, if I had tried this richer adjustment..
Personally: If my top end was running rich and I knew the float levels and other parameters were OK, I'd immediately be suspect of partially blocked air circuits and/or Emulsion-Tubes, . There are 4 rows of 5 drilled ports in each emulsion-tube. The holes are specifically located and sized to inject air at a specific ratio to the fuel. They are small so that the air being drawn through them will produce very small bubbles with no detrimental affect to the flow of fuel. This pre-oxygenates the fuel for better fuel-misting in the venturi and better combustion. Think of an fish-aquarium "air-stone". Lots of tiny bubbles oxygenating the water efficiently. If any of the holes in the stone were blocked the volume of air being delivered would decrease and conversely if the holes were too big the oxygenation would be inefficient. Same with the emulsion-tube. The hole size and number required for optimum performance is calculated. Get a blockage in any of them and you have now reduced the induced- air to fuel ratio resulting in less efficient combustion.
For the effected carb/spark plug: Mixing-air intake ports and their brass metering jets clear ? All 20 ports in the emulsion-tubes clean? Condition of the rubber seal-face and the machined seat in the choke plunger assembly?, Choke-plungers closing freely and fully? Are the "air" ports in the Enriching-valve body clear. Mixing air to both high-speed towers is introduced through the valve in conjunction with the front ports. (Hence when the valve closes during deceleration this air is cut off, giving the richer mixture to prevent backfiring. I've seen these ports gummed up and blocked.

Hope this helps eliminate some concerns and/or directs you to a solution.

Agreeing here with Scotch. Emulsion tubes partially blocked will cause a lot of trouble. The other big thing that almost everyone pays little attention to is the float level. If the float level is off then all of the carb circuits are effected , lowspeed idle, main, transition and choke. Probably the most important check before any of the circuits is to ensure the float levels are bang on.

carbs all cleaned up. found lots of rust particles and dirt.

Flushed the fuel tank to.

Will do the compression test tomorow. I'm done for tonight.

Awesome !

compression test done.

1-145 psi
2-150
3-135
4-152
5-142
6-152

Re the rust and flushing of the tank. Make absolutely certain that the tank has absolutely no rust or other debris remaining ! If foreign material gets into the shut-off valve it will score the nylon cone as well as the tapered valve body causing scratch's and creating a valve that will leak when shut off ! I doubt anyone has the stock internal fuel filter any longer and this is why I mention this point.
A leaking OEM valve can be repaired if the damage is limited to light scratching and not deep gouges. That's another article ! Hope this helps. Good luck !