Dave, I have 2 of the OS46 SF's - both being ABC versions (they were marketed as ABC but I understand they were really ABN) but with the normal carb. I bought my first one in 1989. Well made solid engines with good power but these days they are outpowered by the OS46 FX & AX, also the TT46. Having said that, I love my OS46SF & will never part with it [8D]

To date I've only ever seen pics of the larger bore carb & the pump.

Well done on the purchase !