Since that's a carb'd bike, I don't think you'll be able to get an MPG display for it. As for gears, you can look into one of the aftermarket CVT options, I forget which one, but one of them reduces RPM's at highway speeds by 500 or so. You'd gain a LOT by slowing down from 75 to 65. Even more going down to 55.
I'm assuming you've already done the routine maintenance stuff on it, oil change, air/CVT filter cleaning, belt change, valve adjustment? The belt change is the big one. My Burgman is only getting down in the 50's in the winter temps, during the summer I was into the 70's (with poor aero, as mine was wrecked and never fixed). And I still need to do a valve adjustment and replace the belt and CVT. (CVT pulleys seem to get worn down from the belt itself, the aftermarket units don't exhibit this problem I am told).
Very interesting work you've done thus far, are you planning on dog-housing the front wheel? I imagine that would make for a big increase in efficiency.
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