XJ550 timing chain loose/no tension

The bike is acting up weird, when warm. High idle and what seems to be a timing chain rattle at 3-4000 rpms. I took the valve cover off with the engine rotated to the "C" mark on the flywheel and everything seemed to be fine, the chain tension was good etc, but as soon as I rotate the flywheel to any other position than the "C" mark, I can pull the chain loose. I´ve taken the tensioner apart, put spacers under the spring to help it give the chain more pressure, but nothing.
Maybe the chain only needs to be tight when on "C" mark? But what´s causing the rattle and acting then... Seems very weird.

Thanks
Joosep

 

chain guides could be worn or chain needs to be replaced you should replace guides when chain is replaced or inspect them. the tensioner pushes on guides to tension chain

rattling could be chain hitting the valve cover