This aspect of the LC is the only thing that has niggled since I bought a 1000 mile old one from the local dealer in Oct 2013. The "cackle" as I named it was evident from the start and in spite of visits to two dealers and comments from others, the source has never been identified (or admitted). Some dealers reported that "engine noise" was often mentioned when test riders returned a bike. I have become resigned to this characteristic and now use ACS moulded ear plugs to make the ownership of my first BMW since I had an R100RS in the late seventies, enjoyable.
So many suggestions have been put forward as to the source, but mostly by people who feel they must answer a question. I have heard "It's the clutch now that it's at the front". "It's the automatic decompressor" (Was it designed to rattle during normal running as surely a "rattle" means something is hitting something).
Going back to the original Post: Are the current bikes quieter? If so what has been changed? Do test rides produce no negative observations as to noise? Have you had a test ride recently? If they are quieter, it must mean the source has been found. What was it please!!!!
Incidently mrtee43, Where are you "in the North" ?
We could compare "rattle".