Badunkamunk

i just checked the condition of my spark plugs, they definatly need to be replaced. they are black and lots of build up. while examining the plugs i noticed that on the threads of the plugs that there is oil on the threads. not sure where it is coming from. looked through the maintnece book and couldnt find anything, and searched the forum. is this a common thing on a rotary? are there common placed that oil can come into the rotor housing besides the squirters?

not sure to be worried or not....can anyone shed some light?

thanks