Your carb should be stamped AJ2A which is used on the B1F (Blue streak Single), and S1G, D1G, 1H models. It should have the horizontal “Synchronous Control Arm” part number 1F121 on the “Synchronous Control Shaft” part number 1F114 (post) for synchronous operation when the mag lever is moved. The arm & post are shown in Buccaneers photo on his MS111A carb. This spring loaded horizontal carb lever arm is operated by a metal cam
piece on the bottom of the mag plate. Indicated on the cover and in the parts catalog pics. (post, arm, nut, lock washer, Synchronous Control Cam for mag plate pn 1F140).
Model B1F should be stamped on the front edge near the bottom of the crankcase.