Cold Start Issues

A non functional choke will act just like this and sometimes can be worked around by pumping the crap out of it 4-5 times before you try and start it.
If it doesn't fire, pump it a few more times and try it again.
Of course all the above is basically a work around, but it sounds to me like the choke needs fixed or adjusted correctly.

With it cold and the air cleaner off, pump the throttle to the floor once and check the choke butterfly for being pretty much completely closed.
If it isn't it needs adjusted.

The fact that you have to play with the throttle to keep it running even after it does start is the dead giveaway that this is what the problem is.