These older threads might shed some light on the issue:
http://www.diygokarts.com/vb/showthread.php?t=7528
http://www.diygokarts.com/vb/showthread.php?t=7208
You are missing the tank mounted engine control "quadrant" which utilizes one slide lever for the choke and another lever for the on/off kill switch.
EDIT:
You're also missing about two carb mounting screws. Best to have those installed to plug the holes and prevent leaks.
It's not absolutely necessary but I think the choke control & linkage is very useful for keeping the choke plate from flopping around and closing while you're on the throttle.
You're also missing a steel 'L' shaped bell-crank and a thicker rod that connects to it and to the governor control under the tank but for go kart use, I don't think it's needed at all. That rod is for connecting to a stationary throttle linkage that pivots on the side of the carb, like on a roto tiller where you set the speed and leave it.
If you're still using the governor, what you need are the related throttle control pieces & return spring that are situated under the tank. Do you have them?
Lastly, if you wanna ditch the governor for some real fun, I have a setup in mind that ditches all those rods and levers and uses the Briggs Raptor racing style throttle.