All, This is an update on the clatter from my 2010. Finally had a free weekend in October to open her up and poke around. Started with the rear cylinder and valve cover. Found nothing out of whack, valve train, chain and tensioner all good and all lashes within spec. Later I moved on to the front cylinder, removed the valve cover and WHAM... found a scary scene. Short version is the far right side intake valve's jam nut had somehow backed-off the rocker arm adjuster stem's base and was "captured / caught" between the valve towers, just tight enough to not get jarred into anything below and the adjuster turned enough to have quite the open lash space to the top of the valve. This has been the scary hammering sound. Glad I never ran it after I heard all the commotion.
I've not taken the valve covers off to check the lash because the engine's always been fairly quiet and has too few miles. So, what could have happened? 1. It was an oversight at the factory during assembly (never have I ever)? 2. The dealer's servicing (before I bought it used) of the vehicle... possibly the tech. moving too quickly to make the time deadline? Don't know, but other than waiting 6 mos. to really have time to do any work on it myself, no harm - no foul. Very happy it was an obvious fix and no apparent damage, she's quiet again and back to her happy self. Lucky, lucky, lucky!
I had to apologize to my son, not so much for him not noticing the racket (he'll learn to listen to an engine), but for me getting angry and blaming him for any of it. I've just never experienced this on a (any) bike before. Have a few pics attached of what I found after opening her up.