Great news Roland in finding the 'real' leak site prompted no doubt by RT325 who did correctly query your initial diagnosis. It reminded me of my own error following a complete engine rebuild. I convinced myself I had a clutch actuator arm seal weep (arm enters crankcase from bottom on '75 250B). It turned out to be from the clutch rod adjustment locking nut which I'd only done up finger tight knowing I'd have to revisit it when I reconnected the clutch cable. Oil had weeped past the fibre washer tracked down the crankcase and finally dripped off the clutch actuator arm. Anyway well done on finding/sorting your leak and enjoy the riding. Andy