Pict 34-3 adjustment

Hi All
Got a wedding on sat for my mate which iv'e promised my Karmann ghia. Have been following the carb idle adjustment advice on Rob and Dave's vw page www.vw-resource.com/tune-up.html#idle

When i go to adjust the bypass screw, the big one on the side i cant get it to register much in the RPM wherever it is, other than engine stall when i screw it out to the limits. Now my car cuts out at idle and has difficulty starting when hot. Is there a standar position to set this screw so i can get back to basics. I have set the mix screw to 2.5 turns out.

Im pretty desperate and have not much time, was even considering picking up a new carb from GSF but would these be set up already or would i be in the same position??

Any help much appreciated