Angello yes all engines have a needle valve somewhere. K&B .40 is a reliable old standby that has been around a lot of years and there have been a number of different carburator arrangements both with remote needles like your LA 40 and with needles on the main carb body. If that type it will stick out the left side from the carb itself. Possibly if it is that type the needle is missing or if it is a remote type, the remote assembly is missing. This Remote type is unlike the LA not attached to the engine but made to attach somewhere on the airplane.

Due to the variety of carbs used it will make a differance how the engine is tuned depending on what you have. Therefore for anyone to help, more info is needed. Could you possibly post a picture of what you have.

John