Where did you buy them from and do they have 2 stroke or 4 stroke jets fitted?
In 67-68 all Concentrics
were fitted with 2 stroke jets (by 69 4 stroke jets were introduced and new jetting values for the carbs)
4 stroke jetting changes includes....
Pilot jet moved from being a jet in the float bowl area (2t) to being a press fit bush closer to the welch plug (all carbs from 69)
Change of spray tube from slanted towards the head (2t) to flat topped (4t)
Change of needle jet from being thick all the way through (best way of describing it, but the whole jet is metered for flow) (2t) to only being sized at the bottom, the upper wall of the jet is thinned out and does not meter the fuel (4t) 4t needle having a 0.35 hole drilled across the carb to allow leaning of the mixture on transition to needle jet position.
Needle having 1 ring for 600 series and 3 rings on 900 series (2t) to having 2 rings above the clip positions on all carbs (4t)
The jet holder, holds the main jet and needle jet on one fitting being more bolt shaped on 2t and being fluted on 4t pushing the main jet further into the float bowl.
Once you establish those then it’ll be easier to sort the problem. The original 2t jetting was rich... but not plume everywhere with smoke rich, so I’m thinking that you have 4 stroke jets in there. This will give a lot richer condition especially at needle jet.