Found out it is the return hose/tube. Does anyone know how this is supposed to be fastened at the filler gap?

 

The TLR "return hose" is not fastened to the filler cap. It returns to the bottom of the fuel pump plate. It is the tube without the blue clip in the photo below.

The fuel cap recess has a DRAIN tube attached to it inside the tank - as pictured below.

The drain tube exits the bottom of tank at a brazed junction.

 

Fuel Cap assembly.....

 

Thnx for great pictures and a reply.
I somehow never noticed that the drain tube in not fastened to the fuel cap recess. I wonder how this originally was fastened? Soldered maybe?
Do you have a picture of the fuel cap recess from outside the tank so I can see how this might have been fastened originally?

 

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Do you have a picture of the fuel cap recess from outside the tank so I can see how this might have been fastened originally?

I'm nearly certain the tube is brazed to the fuel tank.

This is not the best detail photo, but you can see the four bolt holes for the fuel cap. The fifth offset hole is the drain. It is on the left side of the bike so that it is most effective when the bike is on the side stand.

Note: In the photo the drain is on the right side because the photo was taken from the front of the tank.

 

Was the complete cap change? If the cap was change it may have been cut or broken when that was done. The drain is attach by weld or it was crimp from the factory, It also could have been broken off due to rust, I say if it is broken off get some fuel resistance hose and push it through the drain hole and attach it to the in tank line to create the venting, you can get to it by taking off the fuel tank then taking off the fuel pump and attaching it back to the metal line. You should post up some picture of the inside of your tank then recomendation to how to repaire it can be given. It is basicly simple and Six5 have shown you the complete make up of the tank and it components.
If the line was cut go to your auto store and get some brass coupling and join the tube back together.

 

Thx guys!
I´ll just plug the hole up for now, until i´m gonna change out the gas pump anyways.