The fuel tank is connected via the fuel tap as shown in this diagram:
http://workshop.nsr-world.com/11kv3lj7/2FK11KV3LJ7/H13Frame.html

The fuel tank overflow drops into a little plastic thing in front of the airbox (is a part of it) and drains out via the tube (part 19):
http://workshop.nsr-world.com/11kv3lj7/2FK11KV3LJ7/I8Frame.html

Part #9 in the above plugs into a little hole surrounded by rubber in the bottom corner of the airbox.

I think these are what you are talking about?