GS500 1999 strange sound in the engine

[Simior]

Hello dear GS500 owners. I was wondering if you could help me with one issue... Lately my GS500 (Suzi) started making strange noises in her engine. There are no sounds when she's cold but when she heats up just a little bit (about 3-5 minutes of riding) it happens. Maybe someone could/would tell me what might be causing these sounds (periodical knocking). More info: it seems that the sound is coming from the top of the engine (valves or something like that), the bike wasn't ridden fast for a couple of weeks (only 2nd-3rd gear). Please, I've searched everywhere, watched every video on youtube and couldn't find anything... Will much appreciate every tip/opinion. THANK YOU!!!

Here's the video (sound is quite noticable): https://www.youtube.com/watch?v=-kGxLMDATu0

[Rallyfan]

Are the bolts holding the exhaust to the head secure?

[Janx101]

Yikes!, tractor-licious! ... almost rough enough to have one header just sitting in place with no tension at all! ..  failing that a stuck exhaust valve and top cover leak?

[Simior]

I'll check the bolts tomorrow, but i don't think that this might be the issue since there are no noises when you start the engine... But i really hope that this could be the case.

There are no visible leaks on the whole block. And all the other things you've mentioned.. Hehe.. Can you explain them in more simple terms/words? My english isn't realy bad, but when it comes to technical terms then I'm screwed :\ (not my native language).

And does it really sound that bad? ;(

Thank you for the answers! Keep'em coming!

What is more - the bike it self runs really smooth, acceleration feels great, there are nothing else to notice (atleast for me) besides the darn noise....
+ The sound stays the same when accelerating.

[HPP8140]

cam knock or cam chain.