im gunna bet that the brass fitting that the float needle goes into is leaking. this can be caused by the bad rubber o-ring that helps hold the fitting in the carb. Another thing is that the floats could be filling with fuel. So pull the float off and place it in gas and wait an half hour and see if they fill with fuel due to a puncture. If its not the float id get a rebuild kit for the carb unless its bran new.