FYI unless the power valve cavity is full of coolant your leak is elsewhere. Most likely the head and running down. Base gasket usually won't show up there because there no coolant in that area.

I can see it leaking from the base gasket. The head gasket is fine. I can see when the bike is on it is slowing leaking out from base gasket. my next question is do I have to remove the cylinder head in order to remove the whole cylinder .