Low rev rattle. Should I be worried?

[MC680x0]

I meant in normal riding. Clearly if it's been left for years then any moving part that normally has travel can seize , can, but this would require a combination of events such as air oxidising metal, lubricant dissolving away or hardening up, lots of things too numerous to mention. But I was referring specifically to the cam tensioner on a fz  which I personally have never come across a seized one but if you think about where it is and what it is, this isn't surprising to me and I've had bikes , albeit not fz , bought after being garaged or neglected outside for many years, still never come across a seized cam adjuster.
More likely to be the technique being used or a worn chain with all the slack already taken up. The OP still hasn't confirmed use of all suggestions posted by foccers , as above