IIRC, If after checking the other stuff (no bent rods) and the end result is swapping parts to raise the compression, you should be able to just swap the cylinders and related pistons without spliting the cases. Just remove the head, slide the cylinders off of the pistons, then remove each piston from the rods by removing a retaining clip and sliding out the piston pin. Keep everything in order in relation to the cylinder it came out of and reverse to install.