What about an electric motor and belt? It probably would not take much of "Rich's" engineering given the impression I get that you have likely something around the place that might work. Would be slick if you had an idler/spring to tension the belt to grab, and release when it starts. I would imagine that 2 cylinder and pull starting it under full compression is not too easy, and or risky in regards to your back.
Would be great if you figured out something, then at least you could run it once in awhile, so many of those end up sitting and seizing up, my neighbor had a good running lincoln with the wisconsin V4, but let it sit so long without running, ended up in the scrap heap.
I'm a fine one to talk, my miller NT 251 is right outside my garage door, has not run since Sept, 2011 ! Need to clean the carb, and should, clean the carbon out of the heads, adjust the valves, ran well, just loves gasoline though.