Can you get another opinion from a different shop?
Hi thanks I will try and get a second opinion but this guy is the only specialise here I’ll take the valve covers off and have a check there is no cracking or tapping sound either thanksHe probably did a cylinder drop test. You short out one spark plug lead at a time and note how much the RPM's drop. Use of a wide scale hand held tachometer makes it easier to tell how much each cylinder drops. This will pinpoint which cylinder is causing the rough idling but it will not tell you what the fault is. If he is telling you a worn off cam lobe then the first thing to do would be to remove the valve cover on the side of the faulty cylinder and note how much each rocker arm moves up an down. If they are all moving the same amount a worn cam lobe is not the problem. Is there any clacking or tapping sound with the engine running? I would definitely investigate further or get a second opinion before making a decision on the future of your Shadow.