Finally got this CT3 in a box put together and running great but I noticed the carb bowl drains all the gas out after shutoff. What would cause this? I pulled the carb and checked the floats and everything seems good. It just pisses gas after i kill it. Weird.
 

By "all the gas," do you mean the whole gas tank? The whole fuel line to the petcock? The float bowl?

Does it do that even if you keep the bike upright and shutoff the fuel?
Or does it only leak when leaned over on the kickstand.
Floats can stick for that last scenario.
 

Yes I have to shutoff the fuel at the petcock to keep from draining the tank after shutting off the motor. Then it just drains the carb bowl.

Sounds like a leak in the main jet area:
www.partzilla.com/catalog/yamaha/motorcycle/1973/ct3/carburetor
parts 6/7/8 in the diagram above. Does the jet holder (#8 banjo bolt) fit well against the float bowl? And is there a washer (#7 gasket) in place?
If it drains the entire fuel line back to the petcock outlet, probably need a new fuel inlet valve (#2, 3), as it can fit badly and pass gas from the fuel line to the float bowl and add to the leak's loss.