How many cc is in a 13.5 hp Honda engine?

Honda 13hp gx390 engine is 389cc but honda have change a lot of rated hp of late for example the gx270 was sold as a 9hp engine but now being sold as a 8.5hp and the gx390 is now sold as 11.7hp i sell engine in my store over in the Philippines i have a loncin 13hp there which is 375cc and a 14hp which is 414cc