Dakar rattling

02 Dakar 19K miles has developed a new rattle on decelleration.
Local garage reckons cam chain tensioner may need replacing.
Been searching forums and there is mention of oil type and viscosity, just changed oil to GPS.
Anyone had similar problem / is a new cam chain tensioner a dealer job or an easy fix?

Check through this list at http://faq.f650.com/FAQs/StrangeNoises.htm to find the origin of the rattle.
If you think it is the cam chain tensioner you can find all the info you need to fix it here http://faq.f650.com/FAQs/CamChainFAQ.htm.
It would be worth phoning a dealer and getting an estimate of the cost, and comparing it with how much it will cost to do it yourself, as it seems to be a problem torquing up the cover nut again without the proper tools.