"Rats!", as our champion Snoopy would say. Or, "Curses! Foiled again!". Or stronger, "
".
I had a bunch of ideas (compression, spark, fuel, is there enough oil on the cylinder walls, but not too much...), but not being there to help, I doubt any of my ideas are useful - I'm sure you've thought of all my thoughts and other things as well, and already checked and/or dismissed them. As others said, let it sit awhile and do things that are more enjoyable, then go back in when you are ready and take another look, or build a drive belt setup like Per suggested for running it in. I've been out of my workshop for far too long now, too busy at work putting out fires, or finding other things that need doing (or are more pleasurable to do), so certainly will not throw stones about pausing this build.
Regardless, there is no disappointment at the effort expended thus far, it's been a great ride! Take care,
BenT