cbr125 forum

Hi guys,
my brother is having some trouble with a rattle noise coming from the top of his engine and I thought you guys might know what it could be
Heres a video https://streamable.com/9i95a

It started quite suddenly after a fairly long ride. We had a look at the engine and the cam chain guides we're quite badly worn so he replaced the tensioner, guides, chain and sprocket just to be sure but it hasn't changed the noise. We also noticed the rocker arms had a ridge you could feel on the face so we replaced those as well. Basic stuff like valve clearance has been checked lots of times.

Here's a picture of the tensioner guide. Both seem to have this uneven wear off to the side, is there anything that would cause that?
https://imgur.com/81491fe9-3170-49dd-a031-6dec485f8d61

I'm a bit stuck as to what to inspect next (unless it's time to dig deeper into the engine?). Does anyone have any ideas?

Thanks.