I just got a BCS 722 tiller. It is a very good tiller; it works very well in my black clay soil. Where I live there is about 2 feet of black clay then 20 to 30 feet of yellow clay; if you run into a rock it was left there by someone.
The black clay has to be one of the hardest soils to work; when it rains there is no bottom; when dry it is as hard as concrete. With a tiller you have to start while the soil is still soft and a little wet. There are people that say that you can not kill turf grasses with a tiller; I am here to tell you yes you can.
The best way that I have found is to start when the soil still soft. Till down to only about 3 inches, just deep enough to kill the roots of the grasses; this will apply even in sandy soil. You want to kill the grasses. If anything is alive all you will do spread the grasses. Keep the depth at 3 inches and till again at least a day apart for a few days; the more times you till the better.
After the first pass it will be easy the next time. Then till to the depth you like.
The BCS 722 has enough power to work my black clay soil. The BCS is by far the best tiller I have ever used. Thanks Shahar for your service; keep up the good work.