i noticed a small oil slick coming from this spot tucked in behind the carburetor boot (see pic). Only seems to be on the right side. What’s back there that would develop a leak?

depending on your bike,, it might have the older style plug, there is an updated version that is a stiffer compound, and with a small amount of sealant, mine isn't prone to leaking. Then there is the better machined plug available from this site

Yep

My experience is half of Dave's.  

Like Dave, the replacement OEM plug I installed in my bike started leaking after a few years.  

Unlike Dave, I haven't installed the Varsy plug I purchased a few years ago.  

I do recall the newer OEM plug being a little different than the original plug, and while it is leaking, it hasn't worsened since it started.  A good pressure wash every 3-4 weeks is enough to keep it clean.  The first plug was a gusher.   It dumped oil down both side panels within 100 miles of riding.

That's a very good point verslagen1.  

Correct me if I am wrong, but the plug you designed is held in place by the head cover, whereas the OEM unit is held in by friction and a small amount of sealant.  

If this is true, one could fashion a spacer that holds the OEM unit in place. Maybe a piece of plastic or aluminum dowl rod. It might be a little tricky to get the length just right.  If it's too long, it could damage the plug or push it out the bottom.  Too short and it won't hold the plug in place.  AND...if that spacer were to get loose...look out!!  

I'll stick with your spacer because it's simply a better design and it's convenient.  It can't back out or get pushed through the bottom of the hole, and the o-rings are replaceable if you ever do a rebuild.   It is the perfect solution IMO and I am so glad you came up with your solution.  Thank you for that.

But, I do think someone could improve the function of the OEM unit if they were smart about it.  Maybe something to keep in mind in the event your plugs are no longer available.

"If this is true, one could fashion a spacer that holds the OEM unit in place. Maybe a piece of plastic or aluminum dowl rod. It might be a little tricky to get the length just right."

Ohio, like this?  Been using this for years.  Use the same old head plug over & over.  Never leaks.  Not as cool as the Versy item, but functional.  I think the stock setup comes loose due to the constantly pulsating crankcase pressure.  This stongback stops that.

Come on Dave , where’s your sense of adventure ? While it may have ruined the rest of your trip , you were safe and with friends. Mechanical things fail , it can’t be helped. I know the feeling of loosing faith in your bike , I fix it , then it’s a new bike once again. I have only a few friends in this area that ride but all have jobs and family , so almost every ride I  ride alone. A couple hand tools and a can of gas and my cel phone and ride off into the unknown. One time I was riding with friends to Laguna Seca for the Grand Prix and my SR 500 lost a piston 45 miles from home , but we got my bike home at we all still got there at different times and by different means. Still had a great time. I believe it’s just part of motorcycling , sometimes you just don’t complete the ride and it is frustrating , but such as life , your new adventure has just begun. If I felt that way I would never ride out of town. I’ll be sure to write a good story next time , my ride gets cut short. Maybe it’s just a different outlook on things. I still hate pushing !!!