I have had 5 vfrs (86 x 2,92,95, 1200 2010) and I don't remember the clatter when hot from the engine at idle. The original 86 engine had a little with bad compression on the rear cylinders and I changed the engine for another and is the same noise. Both actually ran well and did this only when hot. Tappets, balancing of the carbs is all good. Any ideas.
As someone who has owned 4 of the 86s, a couple of 99s, an 09 and now the 1200, I would say that the 86 VFR with the pillow ball cam followers is definitely the most mechanically noisy of the lot.
I own four 1986 VFR700/750F. They ALL have their own mechanical music. After swapping in a 14K 700cc engine for a 17K 700cc unit when changing frames and having it being just as loud at idle... I no longer give a shit. I inspected everything when adjusting the valves and everything, including the the spring loaded cam gears, looked perfect. I have a 28K 700 that is quieter. And a 58K 750 that is the quietest and smoothest. Now I put in my ear plugs (as always) and wring their fucking necks. You know what?... they always sound the same as they each always did, and make the same awesome power. Non issue. Smile. You're on a VFR.