Turns to chnage the RPM or the speed?

For the speed, did you count how many turns you made? If not listen to the engine, turning it up to far the engine will idle like its been given some throttle, if down to low it will idle like its about to cut out/ knocking. turn up til idle speed feels right. The engine shouldn't be rocking too much either.

As for the Idle RPM, you need to run the engine 'FROM COLD' then turn the screw until it sits at 850-900 RPM for best results.