powerband limiter???

i have been ridin with my friend and he has taught me to do wheelies and i have seem to do pretty good in powering 1st gear wheelies pretty close to bp so now its time to 2nd gear clutch. but i cant seem to get it up the front wheel comes up bout a half or a full foot and thats it nuttin else just drops. so i let my friend try
( the one thats really good at wheelies) and he cant even get it off the ground cuz of his weight. he says maybe it has a powerband limiter is this possible could this be due to something else like gunky carbs? i gotta a 99 gsxr 600