Boy do I know the feeling! You clean that carb 50 times, try and start it and boom- still feels like a carb issue. If your sure, and I mean sure, that spark is good and consistant then I would start at the tank and work my way down. I know you've probably been through it a dozen times but just for your peace of mind that its not some simple little gremlin....
Fresh fuel, take cap off tank for testing the fuel system, disconnect fuel line from carb and test flow. This makes sure petcock, fuel filter, and line are clear. Reconnect fuel line if all is good. Next check your air intake. Make sure you have a clean box and filter. Mine was horrible.
You've done the carb. Did you do the Air Screw adjustment? If you dont know, its the screw in the bottom of the carb closest to the engine intake manifold. It is sometimes still plugged, but the screw is under the plug. Screw it in and the unscrew it ~3 turns.
If none of that helps with what you've already done to the carb I would find a friend with a tw and switch carbs for testing.
P.S.- compression good?