You really do need to take the whole thing apart and start from the beginning if you can't start it after fiddling with it so much.
Check all the factory settings for the carb. This includes setting the float using the site glass rather than the level method.
Now find TDC and set your timing at 0 to start.
Fuel filter and fuel line.
When I say start with the basics I literally mean square one. You missed something or messed up somewhere. Don't trust anything that has been done.
I'm fighting the same thing right now but I'm getting close to solving it. Mine will start but dies as soon as I go in gear. Timing had changed somehow.
