cam shaft chain and tensioner ZX6RR 2003

Hi (again)

I was going to jump in and check and adjust my valve spacings but I have since been told most likely the rattly engine is the cam chain - I have been told it needs replacing every 50,000kms by kawasaki. So, can anyone confirm this?

I thought as long as there is tension on the chain (ie the tensioner is working) that it is okay but apparently not. When I replace the chain I have been told to replace the tensioner. Has anyone had any experience with the manual tensioners as they are about 1/3 the price. Also, has anyone used any brand chain other than genuine?

Thanks in advance
Ben