I just got done throwing my engine together ... I really don't see how it is possible to replace that seal without splitting the case! its not a regular pop in seal.. there is about 1/4" edges holding from simply popping out.
Alex.
That makes me wonder if putting a slice from the center to the edge might be the way to getting it out. "THEN", warm up the new one in a water bath until gummy-pliable and slipping it in with a wee bit of sealant on the inside case radius. Of course, you're going to have to fish the indented edge in before flopping the rest of the radius. A quarter turn, when in, should make the sealant perfect...