If memory serves correctly. There is an o ring on it. To check the oil you need to remove the cover. Be careful because there is a spring behind it. You will need to loosen the cable, to disconnect it from the clutch. Once you do the just unscrew it from the primary cover. I recommend disconnecting it from the clutch lever as well. Just don't over tighten it when you reinstall it. It can break easily. Get a hold of a shop manual. I believe they can still be found on this site for download.