Documented religiously on another forum....but taken down by the admin because the excellent research scientist, Warchild, moved over to this board. he's going to update when he has time.
There's an increasingly small chance a motorcycle could be a "ticker". Maybe 1 in 15 for '05s. Valve and valve guide wear after 30,000 miles requires a valve and valve guide replacement. Cause not known officially, but supposedly Yamaha has fixed for '06 with valve seals that let a bit more oil by to keep them lubricated (a well known thing in racing circle). Was probably more of a problem in '03 and '04.
We're all waiting to see.
Tickers usually start to develop 5,000 to 10,000 miles and sound a bit different than typical Yamaha Genesis head valve clatter. Best analogy is steak knives rattling on a metal surface and not just a regular "tick" sound.
Again, don't worry dude. Twist her open after warming her up.