Hello BLKBIRD world. I just picked up a 97 BB that a guy bought out of storage unit. He said he cant get fuel to carbs because he couldn't find the pump or relay. I know it has a vacuumed petcock so I rebuilt it. I can pour fuel in the carbs and the bike fires up. If I pour down the fuel lines to fill the bowls it acts like its starving for fuel. How much vacuum pressure is needed to operate the petcock?