Bikes are usually ridden for a lot shorter distances over their lifespan than cars ever travel so 6K rpm over 10K to 20K miles is not really a big deal. However, if you travel 100-miles/day, 6K + rpm on the super slab over 7 to 8-month riding season is not going to be good either. As a guesstimate, expect a rebuild every year if you are going to place those kinds of miles on a small bore thumper. In addition, as your speeds on these little guys goes up, your FE falls precipitously. At about ¾ throttle for hours on end on the 10 WR 250X during the (2) Iron Butt’s, I was in the high 50, mid 60 mpg range. I could achieve close to that level of FE on an F 800 GS and it would last a lot longer.
Not sure what you have in mind, but when you start pushing small bore thumpers towards their peaks, you are looking at Prius FE like territory and a Prius is a heck of a lot safer and far more comfortable if you are considering huge miles.
Another thing, even while riding with some of the best multi-layered and seasonal gear in the business during the WR Continent crossing ride at > 100 mpg’s, at times I was cooking and at times I was freezing while riding in temps from the high 40’s/low 50’s at night to the 110 degree F range during the day. Bikes are cool and save fuel by the super tanker full but there are but a few that can ride them year round as commuters no matter the weather conditions and still receive better fuel economy than someone driving a much more reliable and safer Prius as an example.
Regarding the Honda 230M, it is not just the rear wheel but sprockets, gear ratios from crank to sprocket, and overall tire diameter. The Supermotard and dual sport 230’s are probably very close to the same but I would have to look at the specs and the tire diameter to make sure.
Read the review on the 09 KLX250SF I rode. I have no idea about the CBR250R since I have not ridden it and arrived at a FE capability just yet. I would love to however
A used bike will save you a few $’s and more than likely, you will lay “a” bike down at some point in your life if you ride. I have had two nasty get offs. One from a drunk 14-yr. old in her parents bomb took me out at an intersection about 25-years ago (no life threatening injuries or broken bones but a night in the hospital was in order) and the Antelope taking me out in Douglas, WY last year on the WR with a busted collar bone and three days in the hospital. Both times I was fully geared with the best in the business and it still hurt like hell.
It is not a matter of “if” but “when”. Just make damn sure you wear your entire suite of gear each and every time you crank her over. You do not even ride across the street without ATGATT (all the gear all the time) because you never know. A neighbor of mine lost his 16-yr. old son about 5-years back when the boy was riding a friends scooter in a local parking lot. He clipped a curb at no more than 15-mph, struck his helmetless head on the curb and was killed instantly. Please, ATGATT, ok?
Good luck with whichever bike you decide and let us know.