I have a zx6r j Model. I started to strip down bike to get ready for track days. As on the last day out it seemed to be blowing some oil out the rocker cover when driving hard. Anyway I stripped it down some bit. Took rocker cover off. One of the loobs on the were shinny. And rest were all black. I taking head off anyway to get head skimmed and ports polished. What would be the reason that they are all black. Was thinking the valve stem seals. And because of that it was blowing oil out of rocker cover. Any help appreciated.