honda cg125. Won`t tick over without half choke?

Hi folks. I`ve a wee cg125, 2005, only 6000mile, starts first time on full choke, after 30seconds down to half. But thats it, even after 10mile 0f riding at 50mph if you turn the choke right off it stops, will not tick over, changed oil, spark plug, (old one was very black..ie rich), air filter, set valve clearances. Any ideas?????