I have an 81 CX500c that is not running correct. After the bike warms up it develops a miss fire that is heard thru the exhaust. It sounds like a puff or small pop like a burnt valve. I have checked the carbs for leaks and replaced the resistor in the spark plug caps with the solid bar. None of this has corrected the problem. The bike runs fine cold and revs freely the only time the problem is present is on a steady cruise around 4000-4500 rpm with the bike fully warmed up. Have read about a diode used to prevent cross fire but have no idea where it is. What do I check next and how do I check it as I don’t want to just start replacing parts with my fingers crossed.