I heard I should Check the spark plug from cylinder #5 for crusty deposits. Apparently the lower intake manifold gasket has a habit of leaking oil into that cylinder.
this is a fairly common problem on the OHV. Usually it can be fixed by simply torquing the lower intake manifold bolts back up to spec. I remember the first time I did this, they were pretty loose. It can be done without taking anything off, though many like to remove the upper intake. Before you tear it all apart, I would suggest just grabbing a torque wrench and a 10mm and 13mm socket and see if the bolts are just loose.