Make sure the fuel tank
is vented. (not plugged) as the pressure from the heat allowing the fuel to expand can pressurize the fuel supply to the carb and the needle can submerge the float a bit and allow this dribble. If you think its a piece of debris in the needle/seat, the pressure from the float will hold it in place, turn the fuel off, run the bike till it starts to pop (or open the drain), then turn the fuel back on. The float level dropping down will release the needle letting go of the stuck debris and the fuel rushing in will wash the debris out. If none of these are the trouble, a new needle/seat is in order, assuming the float hasnt sunk. Some are brass (not sure of the WR) and can get holes and fill with fuel and sink.