You could try using a peice of wooden dowel on the bottom of the sleeve to gently pry up. Or maybe a rubber-coated pair of pliers. Keep in mind, the pliers handle MIGHT damage the sleeve and/or the crank case, so use at your own risk.
Once you get the sleeve up far enough to get a flat-head screwdriver under it on the top, then you can use a screw driver and lift it out that way.
Or you can shoot some PB Breaker into the crankcase between the sleeve and the crank case (hold the engine upside-down and use the spray tube). Just a little bit, and let it run around to the front. Let it set for about 3 minutes or so, then give it a shot.