Q. Is there a replacement for the stock cam chain tensioner?
A. Yes, a manual one made by A.P.E. (American Performence Engineering) www.aperaceparts.com Part No.: ST750GX
The literature for the tensioner does not specificaly say it is for the GS500, but it has been used by many respected members of the forum with no problems. It uses the OEM gasket, installs easy, and works great.
Here is a picture of it installed on my bike.
(http://officespace.dyndns.org:8080/gstwin/manual-cam-chain-tensioner.jpg)
Courtesy Briggs