Today, first really sunny spring day here, after playing with charging, I made short ride. Now I'm sure I need carbs total cleaning and rebuild and sync.

Nice bike!
I had spring for exactly one year ago having a ride on my CB750 K6, March 24. This year probably 2 weeks more to wait so all sand is wiped off the road. There is still snow and ice on the roads here.
If the bike has original ignition: Start with adjusting it before doing the carbs. Point gaps must be equal on both.
verify the ignition on both 1-4 and 2-3 with strobe lamp. Then check points again with Dwell meter, adjust when engine idles and set them at the same number of degrees, as close as possible. 23-24 at 8 cyl setting. (23.2-23.5 work fine)
If your engine had a horrible idle before, it will probably run fine now and you might change your mind about further carb jobs.
Dwell setting is the last detail you must do, turning the ign plate will most likely change point gap since plate might sit loose sideways which will cause different gap when turning the plate.
It is possible to tighten up a loose sitting plate by hammer on the case alu ridges supporting the plate.
See more here
http://www.motorcycleproject.com/text/sohcign.htmlElectronic ignition like Dyna-S and Pamco do not mind if plate moves sideways, no point gap that change. Old points can be fixed to work fine
