Originally Posted by
luker
The banjo mounts on the top tube...there are three slots, right? If there are three places, the bike was intended for a top pull front derailleur. I don't recall for sure(someone else will) but I think that the way that this front derailleur was intended to work was by running a piece of cable housing from the rear set of cable stops on the top tube to the cable stop on the derailleur. you can sort of see the arrangement in this picture from first flight bikes (the derailleur is the same as yours, I think).
If the bike doesn't have another cable stop somewhere on the seat tube, then I bet luker's idea is the most likely to be correct. The boss on the bottom bracket shell may have been for some sort of cable stop which redirected the cable back up toward the derailleur. If you don't find another cable stop on the seat tube, then you may have to find an adapter like that.
