I get 25 with my 2000 KX5. I am geared 13/48, ride fairly aggressive tight and open stuff. Some road/two track included doesnt change the gas mileage much. When I road ride I have found my biek has a "sweet spot" (I think its just as the powervalve is opening) that I cruise at.
The larger tank I bought has been a God send!!
Oh yea, I am stock jetted.
Hope this helps.
Woodsy