Craftsman Model 917.276903 rattle in undercarriage

[RL9144]

Hello,
I have the mower referenced in subject line (Craftsman Model 917.276903) and am experiencing a rattle which sounds like a rod knocking in the undercarriage. When I even slightly put pressure on the cluthc/brake pedal it stops. This does not appear to interfer with the mechanical functioning of the tractor at all but is grating on my nerves. Any suggestions?
Thanks,
RL9144

 

[Rivets]

Check the idler pulleys (items C, D, and E on page 27 of the attached manual) for sloppiness and/or wear. You will have to remove the deck and crawl under to check.

http://c.searspartsdirect.com/mmh/pd_download/lis_pdf/OWNM/L0704327.pdf