My best is 917 miles, 2:30 am to 6 PM, on my ride from Florida to northern New York this past September. Did the last 400 miles the next day and was at my house by noon. Did this on my Speedmaster.
I guess I'm only and very thoroughly average. 725 miles over 15 hours, Detroit, MI to North Bay, Ontario, minimal highway and via the Michigan UP and St. Sault Marie. Dark when I left, dark when I arrived, stock seat! Plenty of 600+ mile days on various machines including sport bikes.