Ok the needle swings on the speedo and gas guage...so we are getting power to the meter...and the gas guage seems to register initially...so I am thinkin the meter is OK...
Heres what we know
The self cancelling signals rely on the speedo..they cancel after you go 490 or 15 sec if you are moving...
The gas guage reads properly after a few miles..so it must want some feedback from the odo??
The odo and speedo simply wont work....if the meter assembly is OK...
SOOOOOO

I am thinkin maybe the connection to the speed sensor has been lost or the speed sensor itself....
Now the speed sensor is located on the rear of transmission...You can see it from the left side of the bike lookin down past the transfer case three wires goin into it..it is held on with an allen bolt

...the wiring from this goes to the speed sensor coupler under the left side cover....
Remove the left side cover.... just at the upper left area under the cover the white plug roundish
3-wire plug assembly grouped with a large square one and a couple of others.....you can follow the wiring to the sensor...
Check this connection..corrosion... loose ????
My screwdriver is pointing to this connector in this pic
All that being said and done in the self diagnoses... if the speed sensor disconnected or short circuited the engine light should stay on or blink four times... so maybe we are barking up the wrong tree here...