I used to get almost 80 MPG, but have since dropped a little. I've had the screen almost from day one.
But now with 45K miles, it has dropped a little so I replaced the MPG sticker with one that says 70 MPG.
that's curious.....on both of my BRs, it seemed fuel mileage improved with more miles (at least so far!)
BioHazard gets about 70mpg if I'm running at least 126 grams of weight.
I think I will drop in some very light weights (15-16gram) for running the mountains around Asheville next month, though.
I'm trying to think of what might cause a drop in mileage on a stock engine....
A smaller circumference rear tire will do it....a lower final reduction ratio.
If your CVT is still stock, very worn rollers will do it.....higher rpms to reach the same speed.
Too high an idle setting will do it....more revs = more fuel.
Valve adjustment will do it....even a BR needs one occasionally.
An improperly adjusted pilot screw will do it....setting a Keihin's pilot screw with a Tach
...is probably the most important adjustment you can do for your engine.
It could be rings, but not likely with your mileage and normal oil changes, since one TR rider here from SE Asia reported good mileage after 125,000kms on a commuter Big Ruckus.
or it could just be the fuel blends we're getting these days....130 "localized blends", with added seasonal variations, according to one source I read.
On a cross country ride, I've found some fuel blends that I would have to readjust the carb to make it run properly if I lived there and had to continue to use it.