You are absolutely right. that ball is not supposed to be stuck there like that. it got stuck by someone overtightening the valve unit into the support. I had the same problem in my carb but i dont remeber hows i fixed it. i can only think of two or three ways that it can be done. First if there is a small hole at the top of the valve you might be able to put something in and push it out. the next way is to use something with a sharp point and pick it out of the valve slowly. the last thing you can try to drill it out. By the way of you go with the second option of tryingto pick it out you might want to use some WD-40 or engine oil to make it easier to get it .
Good luck
chaimv
