Uh.... clean it? Then adjust per factory specs? Usually works for me and everybody I know. If you are 1000000000% you have it perfectly clean and adjusted then buy a rebuild kit for the carb it will have a new float valve.
Even I don't pay attention to every little detail and get burned. Just today I was cleaning the carb on our hot rod XR80 because it wasn't running right. I pulled it and disassembled it cleaned everything really well, reassembled it, set the float and popped it back on. Still not right. I pulled it off and double checked everything and found I had a blocked passage when I tried blowing in the vent tube. A little more cleaner and some compressed air solved everything.
BTW the bowl is the bottom "bowl" of the carb that holds the gas. Get it? Bowl.