Okay Zed!! You answered my question. I appreciate you, and I value your opinion. I have not made my decision yet. For me, the bike is STILL a joy to ride with 17/39. I'm not trying to prove anything to anyone. I'm only interested in satisfying my own curiosities & interests. *FUN FACT: It "felt" really good one month, to realize I was averaging 35mpg(according to the instrument panel), and I was STILL whacking on power periodically, randomly, just being playful. This "record" for me, happened a few months ago when here in California, fuel was approaching $8.00/gal. So yeah, mpg does matter to me because my bike is not a dedicated "track" bike. It's my personal therapy/recreational machine, that I take out to enjoy a pretty California day with. And let me be clear; I'm not "broke", but it still doesn't feel good to me mentally, knowing I'm being savagely gouged(robbed) at the pump, without validation. To me, that's mild terrorism(LMAO ). Have a nice Turkey Day, Zed!! -👌Changing to a 16/39 setup from stock(17/39) will feel dramatically better(acceleration wise) with that "wow" moment since it's like going up 2.5/3 teeth in the rear. As I added teeth to the rear, 16/40 and then 16/41, those changes were more subtle.
To be honest I never track my MPG and just fill up when my fuel light comes on, but like BH mentioned, you're bound to lose MPG when you run taller gearing. Also top end speed will be affected by running taller gearing, with the biggest hit deriving from moving from a 17T front to a 16T.