I had a similar problem coming from the right side. Only happened when warm, usually after shutting down, I looked closely yesterday and thank goodness it's coming from the radiator cap! I was almost weeping as bad as the radiator thinking about having to buy an new radiator, hopefully a new cap and I will be fine. Guess it's time after 11 years.
2001 RC51 Penske, Race Tech, PCIII USB, Jardine 2-1, Woodcraft, Gilles, Galfer lines, Race upper. Track Only.
2006 CBR1000 Jardine S/O, Pazzo levers. Street ride with the occasional track day for fun.