I used to have an older os 40.. I tried 2 and 1/2 turns out from closed and started motor then turned in 1/4 turn at a time until the motor is running at peak rpm... you'll know this when, at full throttle, you hear the high pitch and the slightly lower pitch at the same time.
If the motor is run too lean, it will die if you gun the engine from idle to full throttle, if this happens open it back up a few clicks until it doesn't die anymore.
Hope this helps.