Chances are your automatic choke isnt shutting off. Once the bike warms up the mix is far too rich and it dies.
Once the bike dies, disconnect the choke line from the carb and cap both the end and the carb nipple. Make sure the carb cap is sealing really well.
Now try to start it up again a few times and see if it runs.
If all goes well it will run again. All you need to do is fix or replace the choke.
Failing this I'd say try starting the bike with the throttle held open until it finally fires up and runs. Then ride it for a few minutes without letting it down to an idle.
Once the bike is plenty warm you can readjust your carb screws as per the instructions floating around the forums.