Honda HRR216 Help Diagnosing Sound

Hello,
I recently picked up a used Honda HRR2168VYC.
 
Here is a link to a video so that you can hear the sound that happens when I begin to mow the lawn. 
 
The sound increases and is fairly harsh. I can fix most components, but haven't had this issue in the past so if anyone has a guess, I'll try it out.
 
Thanks!