Join Date: Feb 2016
Location: Budapest, Hungary
Welcome to the forums.
I suggest to use the search function. The cb500 engine is limited by many things, changing the silencer and a PCV would not bring much.
The engine is capable of 53-55 fairly easy, roughly 60 is still manageable, and racebikes can reach 65-66 with compromises on cost and longevity.
Unless you know exactly what are you doing, you'd be better off with an ecu flash than a PCV.