Could be as simple as a hose clamp has loosened up .
Are there any quick disconnects on the fuel lines in the tank area ?
I don't know about the K75's, but the OEM installation of fuel lines on my oilhead, had clamps that were crimped onto the lines , no threaded (worm gear type) clamps, after having the OEM fuel line quick disconnects break, I opted for the clamps that BMW sells for fuel injection lines, instead of the typical 'worm gear' type, they have a metalband that contacts the fuel line, so the grooves or serrations in the regular hose clamp, doesn't cut into the rubber of the lines .