My motor makes a ticking noise when warm.

I adjusted the valves already three times, I also replaced the timing chain, but tickings continue when engine is warm ..

At this point, I am convinced that it is not valves noise and not timing chain,
After a bit of web research I realized the ticking can be from the decompression mechanism ?

Do decompression system can make noise only when the engine is warm?
How can I check the integrity of the system?
I'd really appreciate your opinion