You missed the memo. Fresh rebuilds always have low compression. Thats the purpose of a break-in period.

This happened to me on on a rebuild a couple of months back. It would turn over and for get started and would quit after about 2 seconds. I would pull the plugs, squirt some oil into the chamber and get it started again for about 2 seconds. The part that pissed me off, was that the very first time it fired up, and then I set it off to check for leaks, and after that I could not get it running again. Finally, after getting pissed of with it, I simply reset the timing and the engine fired right up. Moral of the story, always check you timing, even if you don't think you need to.