Rattle and tick..... Rev it Singh.
My G5 is also developing similar bad engine noise, more pronounced than C5 of ironhead. The sound is less when engine is cold and oil is thick, but more when the engine is hot after riding several miles as in the link below -https://www.youtube.com/watch?v=BdAGt_s07XA
Between 28 to 50 seconds of video, I hear a resonating tuning fork sound as if a hollow bell was getting struck repeatedly.
Yeah, I hear that little bit of ringing now Singh. Thats not your rear head steady mount, or your pipe is it ? This is a new sound, and you didn't hear it in the summer when the oil would thin out quicker?..... Using thinner oil for the winter ?
FWIW, it sounds to me like a piston slapping at idle.How many miles on the engine?
Singh, you could try a compression test. Do it using the starter, with a fully charged battery....hopefully the auto decomp won't skew the readings this way. Disconnect the fuel pump and throttle wide open when you do it..... see what you get.