Ok, i couldn't take the camshaft out, but i could see the pin near the exhaust valve rockers, i checked to see if is working as u said,
"the pin is raised above the exhaust cam lobe under the spring tension of the weight mechanism, and (b) that is retracts when the weight is flung/moved outwards"

every thing is working fine, so i closed everything and started the engine.
I was sure that the knocking will continue because in fact I have not changed anything (that I know about).

To my surprise, the ticking stopped! don't know how but I guess what happened is what you said, "it looks like the decompression shaft was inserted 180 degrees out which would mean the lobe on the end of it wouldn't have been acting on the decompression pin"

thanks to you and your explanations ticking are over now.

thank you so much for your help !