Top speed on gz250

[Skunkhome]

I have been searching but must be using the wrong search criteria. I am a big guy (250lbs but loosing) and am generally happy with what I believe to be a Stock GZ250. Performance seems to be fine as it keeps up well with surface street traffic (well actually can run off and leave most autos in traffic if I have a mind to do so.) but I am curious as to just what sort of top speed is typical of a stock bike with a lard bucket like me onboard. What is the benefit of adding a 16T front sprocket. I realize that it woud move my shift points up by 6-7% but other than that would it improve my top speed or just reduce the maximum RPM in overdrive (5th gear). I am quite pleased with the amount torque the bike has now and am concerned that the 16t sprocket might reduce the torque significantly. Another issue is that i do not want to adversly effect my gas mileage. Can the 16T sprocket be installed with the stock chain ?