[Oldsguy]

Bore does make a difference. I don't remember the laws of physics describing fluids under pressure but do remember that innner diameter of a device that handles fluids affects the fluid pressure. So, if you have a m/c with a different bore than the original one the pressure will be different than intended originally, which means in your application the brakes will "grab" too quickly or slowly. You said they don't perform like you would like them to, this may be the reason. You might want to research this a little and perhaps get a master cylinder that is a direct replacement of correct bore.