Army,
Your response has me a little confused. What does "its proper setting mean and what do you mean by backng off 1/4 turn?
Easy way to tune the high end needle valve for this engine is to start with the needle valve about 2 turns from fully closed. Start engine and go to full throttle after you remove the glow plug. The engine will not be running extremely rish. Slowly (while engine is at full throttle) rotate the high speed needle valve clock wise while listening to the engine speed up. The point at which engine speed is at its maximum and further leaning of mixture (clockwise rotation) is called max lean rpm. This is not an optimum setting. Once your engine is at max lean rpm, you should now richen engine by about 3 clicks counterclockwise on the needle valve. Verify that engine rpm dropped about 400 rpm by briefly pinching and releasing the fuel line to the carb after you make the 3-4 click rich adjustment on the needle. If engine speeds up 300-400 rpm you are correctly dialed in. If it sped up only a little, richen another click or two on the needle valve and repeat pinch test. Of course, if when you pinch, engine dies or doesn't speed up at all, this means you are way too lean and need to immediately richen mixture. The optimum mixture setting is about 300-400 rpm on the rich side of max lean rpm.

Good luck and hope this helps.

PS You stationed or work at Fort Useless or are you a Army wannabe (Navy) squid?