With situations like this, you need to be very 'specific'. Folks can make guesses but likely can provide a great deal more insight if YOU provided more (detailed) information.. I suspect, those that can help you would like to know rpm. I gather per your other posts, you do not have a tach. No problem, let folks know the speed and gear you are at when you experience this "surge".
My bike has lots of mods. I as well have played with the carb, but it seems the process is not as yet, correct. I get a bit of hesitation/surge around 3800rpm's. I have not raised the needle as much as others, perhaps this is the issue. As I am not asking the question, I will not belabor my 'situation'.
Guitarman, we likely would profit from more information. Gerry