More details would help. Could be several things. Start with simple and cheap things: 1. Run some Sea Foam in your gas for a tank or two. (still surging?) 2. Drain tank, flush, remove petcock and clean fuel inlet filter. 3. Is the air box stock or modified? Is left side cover on bike? The screw you're referring to is the fuel/air adjustment. Affects idle to one eighth throttle. Use a sheet rock screw to remove tin cover. It's UNDER Carb bowl, hard to see or reach. Rotate carb to gain access. Take sheet rock screw and poke into tin seal ... pull it out. Now you can remove the stock screw and add an extended fuel/air screw. Much easier to adjust with the extended screw.