Ok, I'll try.
The gas gauge is broke and the sight window is deteriorated so bad that even if the gauge was working you would not be able to see through it. The gauge and fuel connector are all one unit.
This tank is not vented through the gas cap, it's vented by the fuel connector. As you can see in the picture it has 3 probes, one for fuel, one for holding the connector on and a third pin that is pushed in when connected to fuel connector. Every fuel gauge unit I've found on the net, is minus the third pin. Apparently Yamaha has done away with that design and uses a vent screw on tank cap.
So that's my problem/quest. Find a replacement with the 3rd venting pin.
I hope this makes sense to you now.