I installed cast iron pipe sleeves in a concrete wall and need to remove at least 3" of the sleeve to get the conduit seal in the wall. I need a way to remove that with minimal damage to the exterior of the wall.

Try a cutting torch, put up protection up around the hole . You may have to cut whole pipe out if you can get to it, if you use a sawzall with a long blade (special for cutting cast iron)

If it is a cast iron plumbing pipe that you are trying to cut off there are several ways to do it, one is to use a hammer and a chisel. Mark a line where you want to cut and then start by putting the chisel on the line and stroke it with the hammer, move the chisel along the line about a half inch and hit the chisel again, you don't have to hit with real heavy blows, just heavy enough to see where you have indented the pipe. Continue all around the pipe, you will probably have to go around two times but eventually it will break at the line you have made.
If the pipe you are wanting to break off does not have a hub on the end you can break it off with an adjustable wrench. Adjust the wrench (I call it a crescent wrench) so that it will just slip onto the pipe about 1/2 inch, after the wrench is in place pull down on the handle of the wrench and a small piece of the pipe should break off. Move the wrench around the end of the pipe breaking off small portions till it is like you want it.

When I say slip the wrench on to the pipe about 1/2 inch I mean onto the wall of th pipe which it about a 1/4 inch thick. And when you pull the handle to break the pipe pull to the outside of the pipe not toward the center.

I hope you can understand what I am trying to tell you. If you don't send me another note.

HEY< Letmetellu, IT is sure going to be hard to break or cut with hammer & chisel being poured in concrete, you miss read the question F. B. E.