Wow, what varied experiences!
I took a nearly 200 mile jaunt on my '03 Burgman 400 just yesterday, and watched the mileage carefully. It was a perfect riding day, cool and dry, on back roads with peak speeds just over an indicated 60 mph, but mostly 50-55 mph. There was one ugly stretch of maybe 5-6 miles with stoplights every couple of hundred yards (it seemed). The terrain was slightly hilly, but not mountainous.
At the end of the ride, at the 194-194 mile mark, my gas guage was at the very low end of the red quadrant just before "E", and the tank took 2.8 gallons when I filled it. So, given a 3.4 gal. (or is it 3.8? I forget) nominal capacity it still had plenty of fuel in it despite the alarmist indication of the guage.
This calculated to just over 69 mpg, which is pretty good, I think. My wife, who rides an identical 400 but weighs about 90 pounds less than my lard butt does, took in 2.7 gallons of gas, for a 71+ mpg rating. This was using mid-grade gas, by the way, the 89 octane stuff.
The scoots in question have about 1300 miles on them.
Has anybody else registered similar readings?