One of the old tricks we used to use was to add about 4 ounces of fork oil into engine oil. The CB500/550s used to leak at the oil passage at the head gasket. Actually had some customers that it helped. I suspect that it swelled up the O ring a little.
In my case, I don't have a compression seal leak as much as it's oil simply bleeding through the head gasket from the cam chain area. It's not bad but after cleaning the motor with mineral spirits and about 50 miles (20 at about 75 mph) of running the motor there is a slight weep both front and rear. It's not from the combustion chambers. This bike probably had the headgasket replaced at one time with an aftermarket one. The composite stuff they use could be allowing the oil to flow through the gasket not around it. We used to use gasgacinch in that area. IIRC honda started using some sort of sealer on their gaskets.