Hi there. I put some liquid wrench, applied some heat and nothing, si I started watching the videos on YouTube on how to disassemble and assemble back the engine and I'm working on it; now; I have a small issue, I was removing the screws on the valve compartment and one of them the head is not good, I don't know if the Allen wrench damaged the screw or what? Anyway, suggestions? With out removing that screw, I can not remove the cylinder head. Regards.