No Noticable Knock
I'd agree with VersysBob.
I've had my '08 since April of 2008, got just over 7K Mi. Never noticed any knocking. If youve got stock pipes, you may just not be used to hearing as much from the engine, as the bike is very quite compared to most others.
Check the oil!
Best of luck.
"I've always been crazy, but it's kept me from going insane." Waylon Jennings