Hi guys

I've been trying to do up an old gs500

It has been off the road and sitting for a while so I've tried to tidy it up a bit. Got it going and has since started to make a tapping or knocking sound around the top of the engine. I pulled the tappet cover off and sprayed some valve cleaner in there (small amount) and checked the timing chain.

It only starts happening after a few minutes when the bike is warm

Could it be a valve or timing issue? Or an exhaust leak hear the

https://youtu.be/G01a4zQomg4

There is a common condition on these engines where the cam(s) will "walk" side-to-side in their bearings at idle when fully warmed up. My 05 does this too, but not as pronounced as in your video.

To check and see if this is the case for your bike, try leaning it over as far as you can to the left as it idles. If it stops or gets much quieter it is the cam-walk noise and you don't need to do anything about it, (as it's not damaging, just annoying).