I started riding in the 90’s, all my bikes have had disk brakes. In fact I never faced any problem with brakes, even with track motorcycles. But I recognize that the first time I arrived to the corner with my new CB500K and I pushed front brake lever I was really afraid, nothing happened, speed was the same, fortunately rear brake works OK so I could enter into the corner. In this moment I decided that first improvement should be new and modern brakes. It’s nice to have a bike as original as possible but safety is the first for me.
Once I removed front caliper I saw the problem: Piston was seized due to oxidation. Maybe it is possible to use original brake system, let's work on it.