I seek your advise on pilot air screw. The pilot air screw on my Mikuni carb ( for engine Kawasaki 340 ) is wandering away from the desired position. I usually try to set it at 1.5 turns out, from fully shut position. But due to engine vibrations it keeps getting fully shut after a few minutes of operation. Is there some way to set at one place and prevent it from loitering around ? Am I missing something that is too obvious ? Thanks for your suggestions.