Brave man and great job! Not going to set any speed records though.
I would almost bet a 10 or, maybe even less HP Briggs & Stratton would be WAY lighter and out perform that OLD lump of cast iron.
Funny thing - even though I'm not a pilot, I was thinking a reproduction of an old plane could be fun,
if it had a more modern engine. With a power curve and weight appropriate to the design and structure of the aircraft, of course.
Of course, I'd probably choose something just a couple of years more "modern" like a Fokker D-7, but that's easy to say since it's not going to happen.
By the way, did you notice that after manually spinning the prop, the guy was still on the ground alongside the plane, pretty close to the spinning prop? I don't think I'd want to be standing that close, but that's the way of those old birds.