It's the right hand side above the powervalve. It's the only vent on this bike that I'm able to find. It currently has nothing screwed into it and I ran the bike briefly for the first time today. There is a long rubber hose that attaches to it. I'm just not sure what it affects without the long hose on it. There is no standing water here in the desert so I'm wondering, while I get one on the way, if I can run it and break in the new piston and cylinder.
Metric nipples aren't super common in town so I'm thinking I'll drill the center out of a metric grease nipple and use that.