I'm no carb expert, but the way Ive always done it is adjust the idle a little higher than normal then turn the screw out so its idling good. Then turn it in until it starts to run like crap, and then back out to where it just smooths out again. Then turn your idle back down.
Mine is doing something similar at the moment, barely idling and backfiring when I give it a little gas. I think I need to clean out my pilot jet. Have you cleaned your carb lately? I had this issue on my DRZ last year, and cleaning the carb and replacing the pilot had way more of an effect than when I just tried to mess with the air/fuel screw.