Without seeing the engine, it's difficult to determine the problem. We don't rely on number of turns, so the number doesn't mean much to us, especially on the idle mixture setting. We start out with both high-speed and idle needles too rich. Get the engine runnng at full throttle and lean to just rich of peak RPM, then retard the throttle and work on the idle mixture.

If the high-speed needle's bent a bit, then it will affect tuning. 3/4-turn is in a bit too much. Normally, we'd see a setting somewhere near 1-1/2 turns out from closed +/- 1/4-turn or so. Many problems are caused by a bad needle seat. If it's been eroded a bit, the high-speed needle has to be turned in to help meter fuel. The only solution is to replace the carb body and high-speed needle.