I currently have 2 Sportster .65's from the Goldberg Mig-27 Army Drone foamies. They have bad carbs so I'm in search of new ones that actually work. Mine were made in 1990 or so, and have no head gasket. Metal to Metal head, and no bronze bushings either.
I am keeping my eyes open for a .20, .28, and a .45 so I can have at least 1 of each size. I'll only buy these engines New as most people dont run castor fuel in them and ruin them.
I'm a big fan of the Sportster engines as well. No planes to speak of just yet... but that will change with time. I love the sound they make.