[MOTORHEAD]

Well I think I've found the culprit ! The port the banjo bolt screws into is an insert of some stronger metal than the cast aluminum of the carb body, and as you hopefuly can see in the pics, there is some corroding away of the aluminum surrounding the insert, leaving it standing proud and providing little sealing surface for a soft metal washer. Ican see why a fiber washer would seal better. I did find some copper washers at the local exotic car shop, they seem to be doing the job, so we'll attempt to tune today.