Need help to diagnose noise in valve tappets

[suzukizone]

My 2000 GS500E, 16,500 miles.  When cold only, lower temperatures (60 deg F or lower) When first starting a loudish noise that resembles a tappet shim "snapping" back into tje top of the tappet happens.  Only one time at starting & not always.  Valve clearances have been set spot on & checked numerous times.

There is a slight circular indent in the head just to the left on the RH Exhaust position that matches the curve of a shim. 

1. Has anyone ever had this experience?  Bike runs fine and only happens irregularly & only with dead cold engine at lower temps.

2.  Sound really resembles the sound of the shim "slapping" into place if it wasn't perfectly seated and the heel of the cam came around and pushed it down flat.

I am passing the bike on to a family member but feel we must get this solved for him.

Please email me direct at     suzukizone@yahoo.com

I am having a little trouble with the newer set up of this site after being away for some years.

Thank you for any help you can provide.  Feel free to ask any questions.

Douglas, Baffled near Baltimore