On my 83 XL600, I discovered another oil leak. Not sure what the part is though. Sorry no pics, but will try to describe it as best I can. On the right side of the cylinder head, towards the rear (NOT in back) there is a flat sided screw head, for lack of a better word, silver in color (stainless steel?). It's about 1" in dia, with a hole in the center, and what looks like a slot for a screwdriver, except it's about 1/2" wide. I checked, and it's tight, but as far as I can tell, it's leaking. Any idea what it is, and how to stop the leak?