air screw, which way?

[elcamino12sec]

which way is rich and which way is lean on 4 stroke carbs? atc 200s?

[TravEX]

The fuel/pilot screw is in front of the slide on the carb (motor side) (4 stroke), and 'in' will lean the mixture and 'out' will richen the mixture.

On 2 strokes the air screw is behind the slide (airbox side), and 'in' will richen the mixture and 'out' will lean the mixture.

To answer your question on the ATC200, 'in' lean, 'out' rich.

[Taiser]

If I remember my old shop manuals, the standard start setting is to screw it in all the way until resistance is met (DON'T OVER TIGHTEN!!!!!) then back it off 1 1/2 turns. Set your idle from there. Again going from memory here! :D