For the guys who's Road Star ran fine and then, without changing anything in the tuning, develops a bad hesitation just trying to move off idle, pulling away OR it seems to just starve for gas when the throttle is opened from highway cruising, check your carb slide. Being made of hard plastic, the slide has a tendency to get "imprinted" with the round shape of the carb bore on it's inboard surface. That is to say that a combination of carbon buildup and physical impact between the slide and the aluminum of the carb itself creates a pronounced ridge on the inner surfaces of the slide. That ridge can cause the slide to stick in place, at idle or steady cruise speeds. When you open the throttle, the engine gets more air, but the slide resists rising and so fuel delivery goes VERY lean.

I've had one RS that fought tooth and nail to pull away from a stop without stalling. Another ran great most of the time, but wouldn't pull past 90 MPH, as if it was jetted very lean on the main jet, when the throttle was opened at highway speeds. In both cases, removing the slide and using a piece of Scotchbrite to polish away the carbonization/plastic deformation on the slide fixed the problem.

This problem has been around since manufacturers started using plastic slides in CV carbs. In fact, I discovered it for myself when it happened to my 1985 900 Ninja, after it had a few thousand miles on it. The high-frequency pulsing of the slide against the carb bore causes the plastic to be compressed, creating a raised outline of the carb bore on the portions of the slide that spend less time in contact with the aluminum. Intake backfiring (common to slow turning, big twins) sends blasts of raw flame, carrying carbon from unburned fuel, up to the carb, bathing the slide in hot carbon.

At least the fix is an easy one. You'll be able to buy Scotchbrite pads at any decent hardware store. Half a minute of polishing will make the slide's inboard surfaces smooth as a baby's bum. Clean it off with a rag wetted with alcohol or Gummout and put it back in the carb. I recommend against using sandpaper, because it is more likely to remove too much material, when all you want to do is to remove carbon and to polish the plastic so it has no hard ridge. The Scotchbrite pad is also easily formed to the shape of the slide, reducing the chance of removing healthy plastic. If the lean condition hasn't been eradicated, maybe you really do need to look into the jetting, float level or fuel delivery from the tank.