Nearly all modern OHC engines have auto cam chain tensioners Spook, unless they're belt driven like my 500 Rotax!
That's not to say that they always work correctly though, and IIRC certain Suzuki ones are prone to sticking, and benefit from some faffing around with the preload adjustment screw to get them working again. All are prone to wear as well, and will only last for a certain amount of time before either the cam chain has stretched too much for the tensioner to work, or the slipper part of the tensioner that is in contact with the chain has worn out, or the spring has broken etc, etc.
It's easy enough to pop them out for inspection though, and all you need is to undo the two bolts holding it into the engine, and probably a new gasket when you re-install it. On the DR350, it's at the back of the barrel at the bottom right as you sit astride the bike. I expect it's in the same place on the GN.
HTH.
