I ventured into the 60 mph range, still on the old tires, it feels like a 750 to me, a little buzzy at 60, 4,500 rpm maybe? I'm thinking I might prefer a few less rpm's than 5,000 at 75.
This ratio may not be stock, I haven't counted teeth yet or even pulled the sprocket cover, I did get the lift cleared off today. I'm leaning towards 18/48.