Why would my motorcycle leak oil right underneath the header pipe after doing a valve adjustment?

looks like it is coming from either the head pipe or head gasket. just did a valve adjustment for the first time but did not think it was that tough! Not sure if I did something wrong Everything looked right and was within spec. the bike only has six thousand miles on it . It is a 2001 kawasaki zx-9rWhy would my motorcycle leak oil right underneath the header pipe after doing a valve adjustment?
The valve cover gasket is the problem, as oil leaks from valve cover gasket around spark plug hole, it flows out a hole that was made just for that reason. It comes out just below the header pipe. Its a drain from spark plug hole so fluids wont build up around spark plugs.Why would my motorcycle leak oil right underneath the header pipe after doing a valve adjustment?
It is leaking oil onto the header pipes, and then continues downward as so many things do. So look above the pipe to find the leak, follow the oil back to its source.

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