Screw on left side of bike on the carb? 750e1

Let me start off with the bike and the limited amount i know about. Just picked it up from a guy who didnt know much about it.. Its a 1980 kz750E1. I have managed to fix most of the issues with it up to this point which was the turn signal flashers, a new regulator, a battery which actually fit in the battery box and the grounded switch to the horn.

The bike runs, starts and seems to do okay. However, when i juice the throttle above about.. 2.5-3kRPM it doesnt want to reset. I can hear the throttle grip snapping back and it hits the stop on the carbs as well. I can reach down and press on that screw/nut/spring which im assuming controls the butterfly somehow and it will idle back down and relax.

The IPC breakdowns list it as slotted screw, nut and a spring. But my question is what is it and what does it do.

Which part are you pressing on in the diagram below? Ed

On the 750 E1 three out of the four Keihin CV34 carbs have individual throttle stop screws. I think carb #2 is the one that is fixed. These come with a locknut and spring and are #s 29, 30 and 31 in the diagram Ed posted. If you are looking at the carbs from the left you will see the #1 throttle stop screw between carbs 1 and 2. A few cm further in you have the vacuum line to petcock coming off carb #2. This screw controls the throttle stop for carb #1 and you should be able to put a finger under it and lift it up and back and removing the finger will allow it to spring forward and down. . If you cant see the ones for carbs 3 and 4 you should be able to reach in from the right and feel them.
These screws only get adjusted when synching carbs so dont change their setting

If you have to press on this screw to get the bike to idle down then it sounds like you need to remove the gas tank,remove the carbs and service (clean and lube) the linkage that connects these screws and associated linkage/mechanism to the throttle cable

I cant think of any other slotted screw in there but if I misunderstood then just ignore this reply.

Good luck