If its the stocker I'd go back to 19mm
16/17 seems too high and it will likely leak out the overflow when on the side stand.
Certain my stock carb was set to 19 and it ran just fine, search the thread for info as it has come up a number of times.
Think OEM spec is 18 but at that level mine would leak out when on the side stand, 19 fixed the problem.
Of course riding style, gearing, altitude (especially if the bike is lying horizontal) will all affect mileage but it should not vary that much on a stock carby - pumpers are another story!
I found that 16/17 does make it leak on the side stand. Dang it. So I'm going to adjust it until it stops leaking. Thanks for the help.