How would you find the leak ? we looked at all the clamps and cleaned inside the fairings and some hoses ? I did think that there was a coolant leak at first but after stripping the bike nothing ?
I think if I suggest something to do, that more than likely you have already done it.
I'll try any way; if you can run the bike until it is hot and the fan is going, (the pressure in the cooling system is up enough to cause a leak, if there is one),take the fairing off while the bike is still running. Watch out for burnt finger's and the sort's. Maybe then you will see something leaking. That's pretty hard stuff to work out, but it can be done. One thing to look at is, if the cap is on good,(DONT!! take the cap off until the bike has cooled, chance you'll get scorched
!). You find the cap leaking, shut down the bike and leave it alone for a while. Come back to it later,(when cooled), and mess with the cap then. The rubber seal on the cap could be bad,(wrinkled,stretched,torn,ect).
I am pretty stumped about this also. I dont think your leaking oil, or using Motul or some other synthetic. Since you have already had the thing appart enough to see this area, I would say that maybe the radiator cap is the possible problem,(you wouldnt neccessarely see a bad cap seal for it is hidden, and this a very small leak?). The other thing to consider is that maybe the insulation on the fairing is soaked with anti freeze, no matter how much you wash it now its gonna smell when it gets hot,(I dont recomend taking the insulation off, just ride the bike until the smell burns out of the insulation, it will eventually ).
Unless you have already done these sort of things and found no problems; thats all the tricks I got up my sleeve's.