Speedfight 2 cooling system

Having cooling issues with my Speedfight 2. Is the cooling system a closed system, or should there be a breather hole in the rear of the expansion tank? I seem to have coolant dripping out of the expansion tank as I ride the bike & the temperature rises very quickly. When at a standstill the temp drops.

 

I think its a closed system, but for the life of me I cant remember, you did bleed it right?

 

I thought I had, but I'll give it another try this morning