Help me diagnose top end knock?

I just bought a fixer-upper 2004 Predator 500.
It has a top end knock that stops at idle after a few seconds.
Im hoping this is a case of a stretched cam chain, but thought you guys might recognize it.

It does start super easy – the moment you hit the starter in fact.
Seems to run well with good power aside from the knock.

Everybody likes videos. Here you go:

As soon as I get hold of my tools (in a storage unit) I’ll pull the timing chain tensioner and see if it’s maxed out, but until then, I’d love to hear what you guys think.

Thanks!