First of all, has ALL required maintenance been done according to the Honda schedule? This would include valve adjustment, spark plugs, timing belt (if necessary), etc.
I don’t understand removing the valve cover to check for damaged valved. You can’t see the business end of the valve unless you pull the head.
Has anyone done a compression test and a leak-down test? This should tell you the condition of the valves without removing anything but the spark plugs.