Actually MJ is quite correct. That carburator is not a bleeder carb and has no air bleed circuit instead it uses the very common double needle system with the main and mid range needles directly opposed.

The screw on the right is a guide or guide pin screw as already explained and the screw on the left with the spring is the throttle stop screw. Note that on this carb (originally designed by Super Tiger) the functions of throttle stop and guide pin are not combined on the same screw. Each screw has just one function.

John