I'm the 3rd owner of this bike and i know the kid before me didn't take stellar care of it, so I'm wondering if it's normal to find a little bit of oil near the washer end of the spark plug threads.It's very thick (suggesting to me it's been there in the heat a long while) and about as much as if you dipped your finger then dabbed the threads. there is also evidence of oil on the neck of the coils. all 4 sets of plugs/coils looked similar.

 

clean them, replace the valve cover gasket and plug holes with the new rubber gaskets..most likely they are just leaking a little