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Did you look at the plugs after you did all that kicking? Smell of fuel/wet?
I don't know what jetting you need at that altitude, but you wouldn't hurt anything by cleaning the carbs and seeing what you have for pilots, mains, and clip positions.
Maybe check what kind of spark you have by grounding the plug to the cylinder and seeing if you have a fat blue spark when your kicking it over.
Compression is aways a good thing to know, also. If you have access to a known "good" tester, that will help this puzzle.
Oh, probably find a good condition carrier on here in the "for sale" or "wanted" categories, or Ebay.