Not as easy as I thought it would be. The exhaust runs right by it. I can see the hole but not inside it. tried to take a picture with my phone, it wants to focus on the exhaust. If it is threaded I would say an allen screw is countersunk in it because it is pretty small. Try again with a mirror and my glasses.
Tried again with glasses, mirror and strongest LED flashlight I have, It is a bad angle to view. If there is anything threaded in there it is recessed just enough I can not see it. If you have the cylinder head off is it threaded?