If you are having trouble with the Vacuum Petcock on this Type of Carburettor it is easily bypassed,
1:Cap the vacuum port on the intake manifold on the right side.
2:Take apart the petcock valve and remove the spring that is against the diaphragm.
3:Put it back together and connect the two vacuum line ports on the petcock to each other.
The Vacuum Petcock only stops fuel flow to the Carbs when the engine is stopped.It's not used on the European models and was probably part of the stricter import rules for the American versions.If your Carb Float system
http://globalcxglvtwins.hostingdelivered.com/viewtopic.php?f=19&t=110
is correct it's not needed IMHO,
Thanks to Ookie Wonderslug on CC's site for this little gem.
From VooDoo Surfer.
Another way to fix the petcock issue is to take the spring out and cut the center of the diaphragms out with an exacto and leave the outside as a gasket. that way you remove any obstructions all together.
Also see this thread for pictures,
http://choppercharles.com/cs/forums/96728/ShowPost.aspx