Yea,Yamahas cylinders are inclined very far forward,especially the early Genesis engines.By contrast,Suzuki's retained a near vertical,classic cylinder layout for a long time.My FZR1000 and my old FZR600 both had the downdraft carbs and heavily slanted cylinder banks.
They probably wont work at all on a B4 or any other vertical cylinder engine since when the carbs are turned horizontal,the floats are gonna be all confused and the fuel level relative to the emulsion tubes,is gonna be way off.