The ball and spring choke stop setup on the DC carburators is a hateful thing. When you try to assemble it, the spring inevitably shoots the ball across the room, where it hits the floor and rolls under the largest, heaviest thing in your shop. That is, of course, if you're lucky enough to see where it went. The flat rate book gives 2.01 hours for this job - 2 hours of crawling around on your hands and knees looking for the ball, and 15 seconds to assemble when you finally get the hang of it.
The ball is just a ball bearing. Now that you know the correct size (by purchasing from Linkert Carbs), take the ball to your local hardware store and buy a dozen of them. A few dollars worth of ball bearings will save a lot of wear and tear on your knees!