273 Commando w/front 4 Spark Plugs Black/Sooty

I wouldn't be concerned about the compression. Balance the idle mixture screws and see what it des. Screw in and gently seat the needles. Unscrew 2 1/2 turns and tune from there.
I would also check with valve sealing. Are cylinder 1, 2 3 and 4 worn out?