Motorcycle Repair: petcock operation, rubber diaphragm, suzuki bandit

Question
I HAVE A 1997 SUZUKI BANDIT 1200S, IT HAS NOT BEEN RIDDEN IN TWO YEARS. I CLEANED CARBS AND CRANKED IT UP, RUNS GOOD BUT AFTER 2 MILES CUTS OFF AND GAS COMES OUT OF TUBE THAT
IS CONNECTED TO BREATHER BOX.I NOTICED WHEN I TOOK TANK OFF
GAS STILL COMES OUT OF PETCOCK.(IS PETCOCK BAD )OR HOW DOES
PETCOCK SUPPOSE TO WORK. I DID NOT HAVE IT ON PRI.

Answer
petcock is vacuum operated, there is a rubber diaphragm than can get stuck, thus not shut off the fuel, or it can get damaged, deteriorated and the diaphragm doesnt work anymore...is the vacuum tube leaking fuel ?
Open the petcock and inspect the diaphragm and the spring, all passages, etc...