As has been already mentioned if it is not on the outside of the bike it must be somewhere on the inside and the most likely route is through the mainshaft into the primary
Agreed - I'm currently having the same problem: trans fluid running out, onto the garage floor (clear - I use synthetic, thick, and smells like gear oil). I also see it dripping off the back side of the inner primary and my primary oil smells like gear oil, not primary oil.
That being the case, what is the most likely problem with the mainshaft seals? Is it necessary to pull the main drive gear to change them?