Hi there. I had acquired this older K&B .20 engine a while ago and am now in process of building a PBF to use it in. I have not flown a nitro engine in approximately 20 years and am unsure of how to tune and or adjust this thing. The things I am not sure of are the carburetor and how to set it. I do not believe that it is original. The needle is very short. Also, the other thing I am unsure of is the rotating larger disc on the needle side that the needle screws into, as it has a + and - as well as 3 lines on top of the carb. Any help would be greatly appreciated.

Also in one picture, you can see that the upper right side lug where the screw screws into is broken off and was missing. Will this be a problem?