Petcock question- Vacuum line

Can anyone tell me which line on the petcock is for fuel and which is for gas and where are they to go...I didn't take a photo. I know..

Here's a typical manual slide carb setup on 4 cylinder bike engines.

Good Luck!

[Click on image to enhance view]

The vacuum line is typically smaller than the fuel line.
On the KZ650 there's a fuel tee between the #2 & #3 carbs.
The vacuum line is on the forward port near the carb holder on the #2 carb. Carbs #2 & #4 have vent port in the same position - the vents are higher up on the carbs.

on the petcock turn it to prime for a second and you'll figure out which has fuel coming out real quick that would be the one your looking for.