i think it might be a mixture of the two.the gasket is defo not right and it came off way to easy,dont think the black stuff is carbon,it feels a bit rubbery so think its some sort of coating on the std yam gasket ,the replacement ones i`ve seen look to be copper,head was torqued down correctly
as for the valves,iam going to try my valve spring compression tool tonight,not sure if it will fit at mo.
i`ll know more when i get the valves out
as a little treat to myself i bought a new torque wrench today as old one not to be trusted any more,got myself some new hex drive sockets aswell ,my old omes were only just long enough to remove the head bolts
new ones a bit longer....bought at MACHINE MART in tower hamlets.....my favorite shop