You can't always save the cylinders depending on how stuck they are. Heres the steps...
Phase One: Finding Daylight
The First thing you got to do is get the cylinders broke and physically separated from the case. I used a 1"X12" peice of flat iron, and put that under the edge of the jubs, and start banging with a big A$$ hammer. On the right side you have a good spot right where is says "736" on the jugs. On the left side you have the area to the right of the points. Alot of people use a 2X4, which will work, but it often will start to chip and slide off. You can start by tapping lightly and hoping it breaks free. At some point you have to make a decision to just pound the crap out of it, broken fins be damned.
Phase two: Pry time
This involves using two hammers as pry bars. If you have two full size pry bars all the better. I had the motor on a small bench, then position yourself behind it. One hammer in front, and one in back- with the pry teeth between the case and cylinders. Be gentle as you can, cuz you want to gouge up cases as little as possible, but it will happen. At this point, what have you got to loose right??? Now push the hammer in front forward, and the one in back toward you causing upward force on the cylinders. This "should" force the cylinders away from the case. This should get you 2 or 3 inches of space between the jugs and case. Now on to phase 3.
Phase three: Hammer Time
Now in phase three you have two options. Both are traumatic to the pistons and rods. At this point you should have a since of which piston(s) are stuck. This is the piston you will want to bang on. Get yourself a 1X1 piece of wood about 12" long, and place it on the stuck piston, now whack it with a hammer. The idea here is as you force this piston down, it will slowly move the cylinders up and off the pistons. If this doesn't work your last resort is to place you 2X4 or rod under the pistons, and start whacking with your bigg A$$ hammer. In the process you will break fins, and various other pieces of aluminum will go flying. Don't sweat it, at this poin your relegated to getting another set of jugs any way. As your doing this be sure to the cylinders evenly creep up all for cylinders. If you bring the cylinders up unevenly if can put undo stress on the pistons either damaging the pistons or the wrist pins.
Few more things to keep in mind.
>You should clean both the area between the cases and jugs, and any crap thats in the cylinders above the pistion out before you start. All this crap will fall right down in the case when the jugs come off.
>Again be mindful when/if you use the pry bar technique. You can gouge the case when can leak oil if that mill ever makes it back on the road. The are between the case/jugs is now high pressure and usually not prone to leak, so you have some leeway, but again the less gouges the better.
>I haven't put any hard miles on any motors that I'm banged on the pistons this way, but you have to think the beating and banging could cause a catastrophic failure of a piston/rod if the motor makes it back on the road. Be mindful of this and don't build any 100HP beasts with a motor thats gone through such trauma.