Depends which OS.12...OS-Speed Fact. tuned TZ.12 factory settings are needling (slow speed valve) screw in/out until the head of the screw is alligned with the casing. The idling adjustment valve is the same. The needle vale should be 1.75 turns turned out from the fully closed position. Those are the regular settings.
My terminology for the different valves may be a little odd as my manual is in Japanese, but the TZ engines should all be the same...
Best of luck!