OK you do not have to remove the gas tank to remove the carbs, they fit thru the side once you get them broken loose. While you have them out, also service the intake throats as they can develop holes, and the rubber o ring gaskets underneath can deteriorate. You will also find a lot of buildup on the mating surfaces.
Now if you are removing the tank, you will want to remove the rear tire and the rear subframe to get to it better...