From a REALLY cool site with historical images of all kinds called SHORPY.COM The Caption reads “Fred “Freddy” Fretwell of Washington on a Harley-Davidson”
Fair warning. Don’t go over there unless you have some time to kill. It’s addictive.
Here’s a great grandstand shot (of a car race obviously) to give you an idea of the scale of the the track sizes. Pretty amazing. Must have been quite a spectacle for it’s time.