[Orchestr8]

2021 GTS, just purchased.  Should have a 9 gallon tank, but my gas gauge seems to funtion on a 4.5 gallon logic, meaning it indicates empty and the light turns on, even though it only takes 4.5 gallons to fill it back up.  I have done this now twice in a row.   It seems that I can just continue to drive, but now I am blind as to the real fuel level.  Any ideas?

Yes, that's very common on fuel cells. On everything from bikes and trikes and mopeds, I'm working on a fix. but its too much fun right now to do it. Normally the float in the tank is actually set below the fluid level or at an arbitrary location.  I normally set them up so 1 gallon left and the reserve light or the gauge is dead on E  then I know its 40 miles to get to gat station left. There are few diff type senders. but yeah i agree. Its actually a indicator that goes more than 180 degrees look closely 270 degree swing till empty on 2022 VV .  requires pulling rear wheel and swingarm pulling fuel cell and draining and filling with exactly 1 gallon then make physical or electronic modifications till its right on E.  
Keep in the loop, surprised no one else seeing that anomaly ugh.   not a fun one to work on!  Also the fuel cell is to left of the battery viewed from back.

You are not alone mine does the same thing....I have never put more than 5 gallons in !!