So i had to pull the cylinder head off of my F4 to repair one of the spark plug threads, and now i'm putting it all back together. Anyway the factory service manual is telling me to get new orings on the camshaft holder and a new gasket for the valve cover, but they are both rubber parts. I have never worked on these high performance bikes before, but for all my automotive applications i pretty much always re-use rubber gaskets/orings. So is it really necessary to replace these? Are they going to leak soon if i dont? It's another $80 or so in parts that i dont want to spend if i dont have to.