Hi, Yes I replaced both seals without splitting the engine. One seal sits in the disk valve cover and the other sits in the magneto plate that sits behind the flywheel. (the flywheel cover bolts to this plate) I replaced the O Ring in the disk valve cover just as a precaution even though the original looked ok. Obviously, I have been unlucky in my attempt to minimise the work as I now have to split the engine to replace the sealant. I originally thought that there was a gasket between the two sides of the engine.
Cheers Chris