-what is your ground level altitude? (these engines are set up to run near to sea level if your altitude it much higher than that you will need to re-jet the carb)
-what is your areas average temperature? (if you happen to live in Alaska or on a mountain your engine probably just needs re-jetting like i said above, but also will need a good warm up before it can run properly)
you also may want to give a visual inspection on your choke by removing the air filter, there may be some damage to the choke itself causing this (i.e. a misaligned choke plate could cause 'full choke' to not actually be full choke, and 'choke off' to be more choked or something to that effect, easy to fix if that's the problem.)
and finally have you tried fiddling with the fuel adjustment screw?
this thread is discussing how to gain access to the fuel adjustment screw
edit: oh also if you have less than fifty miles on it it may just need breaking in, i have about the same run time on mine and I have already noticed that it is starting easier. what I'm saying is that small motors really pick up after they finish breaking in. you issue may just be tight tolerances and being set too lean combined, so a little fiddle with the fuel screw, and some more miles on it may solve your problem. I say for step one look at your choke plate to make sure it's good. if that's not the problem then try the fuel adjustment screw, if that doesn't help you may need to look into a new jet or even new carb.