Maybe the first thing that needs to be said is that turning the adjustment all the way IN, LEANS it. Turning it OUT, richens it. Maybe some of your other engines (like Neptunes?) had carbs that worked opposite of this one? Some do. I agree that the question needs more clarification. When, and with what symptoms, does it run lean, to your knowledge? While you chew on those thoughts for awhile, another couple of thoughts comes to mind: As Fleetwin established awhile back, 6 hp OMCs have been built with at least three different high speed jet orifice sizes, for reasons unknown to us mere mortals. You haven’t mixed and matched carburetors along the way, have you? Also, how is the throttle pick-up adjustment set? The throttle plate shaft ITSELF, should just begin to move as the cam follower lines up with the mark on the cam on the mag plate. Sometimes there is considerable slack in the mechanism that needs to be taken into consideration.
Long live American manufacturing!
