Well, I am not sure that that is the source of the noise, but is not rare.
Check this similar thread:
http://www.ninjette.org/forums/showt...t=CCT+motofool
There is no way to "see" the tension of the chain after the valve cover has been closed.
You can find directions in the Top End section of your repair manual.
This is not in the manual, but it is critical:
http://n4mwd.blogspot.com/2013/06/ov...ts-during.html