Hello Dennis, without the flats on the top of the head this does make removal a bit problematic. For starters, a heat gun would certainly help. I would tighten the glow plug pretty snug first. I would then put on some gloves and heat the case at the point where the cylinders threads into the case. I would rotate the engine during heating to assure even heat. While holding the engine with one hand and a glow plug wrench on the head see if the entire cylinder screws off without loosening the head. If the head comes loose, your going to need make a jig from two pieces of wood with two semi-circles cut out of them. Clamp the cylinder between the two blocks in a vise and try and unthread. DON'T use pliers. Ken

I drill a block of wood to match the cylinder diameter, cut the block in half and clamp the whole thing in a vice.  Plenty of control and friction, no damage to the fins!

Thanks guys, I'm going to try the split wood block trick after soaking the cylinder/muffler area with penetrating oil overnight. Nothing ventured, nothing gained.

It came apart easy using Larry's method. I probably didn't need to use the penetrating oil.