
But you already can go at the speed limit at 4000 rpm.  All you need
to do is to find a road with a 35 mph speed limit.

This isn't quite as silly as it sounds.  If you take a nice day trip
over back roads (*not* highways full of people trying seriously to get
from here to there) then you might be able to hold 35 mph comfortably.
You could easily do 500 miles over three different weekends.  You
might even get to enjoy some of the scenery.  Yes, I know this is
probably not why you bought a 250 called "Ninja."