Check the o-ring seal located on the oil filler cap. They are prone to falling off. I had a phantom leak that was driving me nuts. My right pants leg would get "misted" with oily residue. O-ring had flown the coop. There was residue around the head area, leading me to believe the source was from the head cover gasket, one of the head cover bolt grommets went bad, poltergeist....
Might also want to check your shock for leaks, as well as the fork seals. Either of those can deposit traces of oil on the head.
“many a trip continues long after movement in time and space have ceased”- Steinbeck, [I]"Travels with Charlie"
[FONT="Century Gothic"][I]Sometimes your only available transportation is a leap of faith[/I] [/FONT]