With dual carbs on a single cylinder there's no need to synch the carbs, just get them close but tune them evenly so a simple cable splitter would work, but if you wanted to gain something from dual carbs it could be done better by using 2 smaller carbs to flow like a bigger carb, but it would take 4 14mm carbs to flow the same as a 28mm carb, dual 14's would flow about the same as a single 19 or maybe 20mm... the math is somewhere to figure it out more exactly.
how could running 2 14's benefit over a single 20? If one was to set them up to open sequentially or progressively instead of at the same time the effect would be similar to a modern 4 barrel carb on a V8 where you use the small side for cruising efficiency and better low rpm throttle response, then open it up more as the rpm goes up to feed the demands of the engine and make max power. If one was to run a progressive multi carb setup with maybe a 10mm primary and a 15mm secondary it would give stronger starts until the rpm comes up then the throttle could be opened up to bring the secondary into play for a strong top end.
It would definitely take some tinkering to get the air fuel mix right across the rpm range, but it could be done... Actually a better idea would be to set up a 24mm cv carb to run on your engine and set the slide rate so it never bogs, but not so slow the throttle response would suffer, that way you could crack the throttle right from the start and have the same good low end torque and smoothly transition to high top end power... Again, lots of tinkering involved but the outcome would be better than any multi carb setup, just gotta determine the right size carb you'd need for the best top end power and rpm, then get a few extra slide springs so you can play with higher or lower spring tension until it delivers smooth power. i'm sure there's a reason CV carbs aren't used on most 2 stroke engines, but it would be an interesting project for someone who has both the time and funding to try and get one to work right.