OK, I will be dealing with a couple of best guesses here. First, I forgot to ask for the primary gear reduction, the best guess that I have is 64/19 (3.368). Then I will use a standard 100/90-19 tire and use "perfect world" numbers to get a circumference (knob height, tire pressure, and soil type are just a few possible factors that I am ignoring).
So, we will be dividing 11200 engine rpm by the primary reduction of 3.368 to get an input shaft speed of 3325 rpm. We now apply the 5th gear transmission ratio of 1.087 to learn that the output shaft is spinning at 3059 rpm. Factoring in a 14/52 final drive gives a wheel speed of 823.58 rpm. After doing the math for wheel diameter (90 mm sidewalls on a 19 inch wheel, 26 in total diameter, 82 inch circumference), the theoretical top speed is 63.92 mph.
With everything else remaining the same, but swapping to a 13/49, the theoretical top speed becomes 62.98.
BTW, the larger cogs could have the positive effect of smoothing acceleration and deceleration, extra rotating weight isn't always a bad thing, just ask the woods guys.