The carbs you have, if not worn out, and you don't have an air leak, will take you well past lose your license speed. You need to think of them as four carbs in one. Since it starts and idles, the first part - pilot circuit is probably close. It works up to about 1/8 throttle. From 1/8 to 1/4 throttle, it's the slide cutaway which - 3-1/2 stock and if 3-1/2, no need to think more about it. Next is 1/4-3/4 throttle. This is the needle jet, needle, and needle position. Since most of the time this is where you are riding, the needle wears and to a lesser degree, the needle jet. Finally, 3/4 throttle to wide open is the main jet - you are most likely riding here (or won't for long on the street).
If you are having trouble between 1/4 and 3/4 throttle, a simple thing to try is to put the needle clip in a different slot. The lower the clip on the needle the richer.
If it gets better - good, if it gets worse, go the other way.
Saying mid-range doesn't convey useful info. It's best to mark you throttle so you can say are what opening you are having trouble.
Of course, there are many other things other than carbs.
Do you have points of electronic ignition. If electronic ignition, which one. Is your battery good? Are your valves adjusted?
From about 3500 rpm to 6000 it should pull very strong. Explain more about what it's doing.
