Trojan Boat Forum

Until a few years ago, rotating the idle mixture screw (on just about any caburetor) counter clockwise always meant that more air/fuel mix would be discharged and a richer idle mixture would result. But when the bureaucrats in Washington began increasing their stanglehold on Detroit, carburetor manufacturers found that a new system offered advantages in meeting emissions standards. Some companies incorporated a second air bleed into the idle system, which was adjustable. .... Carburetors incorporating this system are commonly referred to as "reverse idle" models since the engine receives a richer mixture when the screws are turned clockwise. Identificaiton of a reverse idle carburetor is usually facilitated by a special tag containing an arrow indicating the direction that the screw should be turned to obtain a leaner mixture. To further complicate the issue, some reverse idle carburetors are equiped with left hand threaded adjusting screws, so they still may be adjusted by the counterclockwise lean procedure.