fuel gauge problem

Not sure if anyone can help but mate bought a 2006 bandit 1200 which i have been going over for the past week, took it for a ride today, filled up at servo and off i went, took about 500 meters for the fuel gauge to read full. last 2 bars reluctant to show up staright away, so 170ks later first bar goes out, not convinced that the fuel consumption is that good, back home and checking the float in the tank, floating as it should be, pushed it all the way down with screwdriver and let it come back up not sticking, put ignition on and  did the same up and down with the float but  gauge stayed the same 4 bars on, lifted tank and disconnected sender connection, gauge stayed the same, turned ignition off and back on and gauge registers empty last bar flashing, reconnect float connection doesnt change gauge still flashing, turn ignition off and then on again back to 4 bars  even with tank on and angle ??

dont worry have since found out thats how they work my 2010 is exactly the same,  may still have a accuracy problem with the sender.