i have a really crude design, Jawa 350. Has a consumption around 50MPG. I rode the old version (jawa modell 634) for about 20000kms and it was usually around 45mpg. (older carb and point ingnition (very poor design, needed check and setting every 600kms))
the point about the oil cost is a good one. never thought of it this way.
My GS 450 needs an oil change every year. 2.5-3 liter of 10w40 bike oil. The Jawa requires very simple 80w90 transmission oil, 1 liter. there is a difference...
But i have to tell, if it's about ecodriving, the Jawa would not be my choice. I'd go for some 125 4 stroker for the everyday communting. But since I do not want to buy a new bike, I use the Jawa anyway.
would love to push the consumption lower though... but do i drive it enough for investing a lot?