either the float needle is stuck or there is a blockage before the needle. did the bike sit for any length of time? pull the float bowl, and the float-needle, turn on the gas,, if it is a small blockage that will clear it. if it doesn´t tear down the carbs. if you don´t want to tear down the carbs try pulling the fuel line and blowing compressed air backwards through the system,, it might work ,, but will probably lead to carb teardown when the blockage is blown to the rest of the carbs.