yamaha xt125r not even getting 60mph on straight

hi i dont know if im having a problem with my bike but its not even getting 60mph on a straight road but i am using a carb off a suzuki dr 125 1982 and that seems to work better than the actual yamaha carb that came with it. the carb that came with it didnt work properly it kept boging out at top end speed and pulling off and it wouldnt tick over properly either. then i bought the same carb for the bike off ebay and that one was worse than the first one that came with it. but with the suzuki carb im getting about 54mph on a straight in revs about 7500rpm and that all i get but i should be getting to 10000rpm and i dont what that is in mph? any advice on how i could make it a little faster made be to get it to do 65mph