Motorcycle mileage

[Sludgy]

I have a 2002 Honda XR650L.

So far I've put street tires on it, filled it with 5W-30 Mobil 1 oil, reduced the idle speed, removed the brush guards, and overinflated the tires. I coast rather than use engine braking. With careful driving after these mods, the mileage went from about 48 to just over 50 mpg, maybe 52 on a good tank.

The mileage doesn't vary much, regardless of whether I drive on the highway or in traffic. I don't understand it.

And I don't understand why a single cylinder 650 cc bike would get such crappy mileage. Harley Sportster 883 twins are rated 57 mpg highway. Shouldn't the smaller, lighter bike get better mileage?

I'm stumped as to what to try next. Anybody know of closed loop EFI for motorcycles?