I went out today for a 120ml ride with the new 16th sprocket fitted.
My comments here are relevent to me riding my bike, how I like to ride it, on the roads I like to ride on.
It's difficult to easily describe the difference in feeling with the longer gearing. The gears are lengthened out a bit so you don't need to get rid of the first three gears as soon as you get moving, they have now become usable. The top three gears are much better for faster riding as you now have a choice of gears to use, where as before anything after 70mph it would be top gear.
I would have expected the bike to feel a little less lively with longer gearing, strangely the the bike feels a bit quicker accelerating, I only have that unreliable arse dyno to go by. My thoughts are that as the 650 is a torquey engine the longer gearing keeps it in the torque sweet spot for longer, I don't know, the bike just seems to keep accelerating for longer.
I think that, for me, it is the perfect gearing for my type of riding as the bike feels less buzzy and now when you go for that extra gear it is actually there.
In the interest of science I tried to see if the bike bike would struggle in the top two gears at higher speeds. Not in the slightest, 7200rpm in fifth and 7000rpm in 6th showing 115mph, I don't think I will be going there again in a hurry as after 100mph the bike was rather unstable. An indicated 80mph is now at 4800rpm.
Would the 16tooth front sprocket suit everyone? maybe not, if you do a lot of hilly two up riding or slower city riding the lower gearing might be better.
Any change in fuel consumption? I haven't a clue, maybe when the novelty wears off and I stop riding like an idiot ( unlikely) I may see a difference.
I would say to anyone, give it a go, as it is cheap and easy to do.