By this time I've forgotten all the story, but are your valve guides OK, and the valve seals? There's oil on top of the head that could be sucking in on the intake stroke, and exhaust could blow by on the exhaust stroke. That would put oil in the combustion chamber and exhaust in the crankcase. Your compression would be OK. The rings and bore would be OK too. You'd think the exhaust would go out the port and pipe, but there is some backpressure from a Honda muffler.