Forgive me from asking some obvious questions, like details abut the bike. Year, stock, modified, etc.
I've owned a bunch of CB750s, and they all seem to have fork seal failure on the brake leg. I've never owned a bike that had a blow fork seal on the side which did not have the brake caliper attached. Sure the could be instances such as rusty for tubes, but typically both do not fail at the same time.
How long since your last ride on the bike?