Surprise Fuel Leak

[Little Red]

So I'm on my ride to Alaska adventure on trusty 1994 K75 standard, in the middle of the Cassiar Highway and after I fill up, (gas stations are 150 miles apart) I notice liquid forming a puddle under my bike and dripping onto hot exhaust.  I panic, thinking I split a hose somewhere and now I'm hundreds of miles from any city, so remote there is no cell service, no electricity or phones (station ran on generator).    After some head scratching and tilting of bike I finally realize that I had previously overfilled the tank and fuel must be exiting from a vent somewhere.   It wasn't oil or coolant dripping.   With the bike vertical the drip stopped. and I forged ahead to the next gas station (150 MILES).  No further problems with the bike but the highway was flooded out.   I backtracked 450 miles and took a ferry to Sitka and counted the trip complete.

Where does the tank vent exit?

[Grim]

On the under side of the tank just right of center is two connections the forward one is evap that connects a hose to the block under the radiator the rear is the drain from around the tank fill. It connects to a hose that routes behind the right leg. These are often forgot when the tank is removed.
Search "air accumulator cup" and you will find an alternative too these lines. There is an occasional issue with over fills dumping fuel into the crank case and the cup is a fix for that. 

[Westone]

I recently became acquainted with the under tank vents on my K75S. I discovered a section of hose that ran from connection on the front of the block under the radiator which had been cut, connecting to nothing, where it used to run to the front vent on the tank. I just installed the air accumulator cup, which was less than $3 if I recall correctly. The cup sits on the frame, and when the tank is mounted properly the vents sit right in the cup. Installed a rubber cap on the block vent.

[WayneDW]

 The cup just makes it easier to pull and replace the tank but whether you have one or not, the overflow line should eventually end up down at the right foot peg plate area and not on the side of the exhaust pipe.