I have a 2009 Honda shadow spirit. It is supposed to have a vacuum actuated petcock valve but the only way I can start and run it without hammering throttle or pulling choke is only if I disconnect the vacuum line from petcock? If it's running and I put the vacuum line back on the petcock it dies. And it wont start with the vacuum line on. Also if the line is off the petcock but still connected to the engine and its running, if I put my finger on the end of line I feel vacuum but it will die if I hold my finger there long ber than 2 seconds .