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Here is what the two-spring system should look like - Briggs call it "governed idle" (it saved them the cost of having an idle speed screw and a tapped bell-crank on the throttle butterfly). Note that in your picture, the throttle butterfly is wide open. If you gently push the air vane lever (the white plastic bit the left end of the governor spring connects to) towards the left, the throttle should close. When the speed control is set to minimum, it should be just about closed with the engine stopped. If it isn't, find out why. Is the bottom end of the speed control Bowden cable properly adjusted and anchored?

I suggest you read right through this thread:
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=33135&page=1

In that instance the problem was a bent link between the air vane and the throttle butterfly, but yours does not look bent. I doubt the missing idle spring is the problem, since Briggs built them for decades without the second spring, but by all means fit the spring since the Sprint engines did have them.