2006 Kodiak 450 engine knock

Hello all,
I have a 2006 Kodiak 450 that I bought this weekend with an engine knocking sound. I first thought it was a valve problem but the sound does not originate from the valves. I am thinking that it is the crankshaft bearing. How to I determine for sure, before I tear down the motor?
It runs great, no smoke, and plenty of power, just sounds like a jackhammer from inside the motor.
Also does anyone have a service manual for this machine?
Thanks in advance for any help
Michael