I went ahead and looked it up.
Download the service manual for the gz250. Linked on this sites forums.
Open manual and go to section 4-4 (fuel and lubrication system)
Third image down reference by the '2' "Vacuum hose"
You don't have to remove the carb but that image is showing you the side of the carb
that faces the engine
'You have arrived at your destination' XD