Very interesting machine. The somewhat lengthy video, "Part II", finally cuts to the chase and is well worth the watch.
The builder did a "Part I" video also giving detailed facts about the materials and components gathered, machined, and assembled, to make the project a success. if you're interested here's a link to that one . . .. You will also see him on his Velocette!
To just enjoy the start up ritual and ride here is Part II. You won't be disappointed.