I did not have the throttle open, so I will retest it and will follow the instructions from the article.  The bike only has 2,983 miles on it so unless it was really mistreated or something went terribly wrong, I doubt it really needs a rebuild.  Thanks to everyone for the suggestions.

While i fully agree with AUTOMAN #9 re fitting it direct in. Herte's a pic of my genuine yamaha gauge which does the job ok. Somewhere i have 'boring video' of using it although only a fleeting view in a video. & spinning with a drill because what i was testing had about almost nothing at turn over & need the drill to start it haha.
photos.google.com/search/_tra_/photo/AF1...obzCy7pjQese3Dg_vNMh
photos.google.com/search/_tra_/photo/AF1...ExscWVrP-4lO3rUXbPE6
Try these links below as i think the others may not work. 
photos.app.goo.gl/brWsmE68ZPobkUzU8
photos.app.goo.gl/spSsWuvK9V1VkFgE9
 

Here's the boring vid but shows tester at the start. Can slow youtube down to 0.25 speed to get a bit longer look.

@RT325: Thanks for the pics and the video. That bike is very cool.

I tried to check the compression per the article. It says: "Put your machine in 1st or 2nd gear (use the same gear each time), and push the bike at a walking speed for about 10 feet."

I tried that, but the back wheel is just locked up and won't turn. Which makes sense to me. How can you push it in gear? Am I missing something here?

For now, I think I'm just going to move on to other things and assume the compression is ok. The petcock (brand new) is leaking like crazy. It's a cheap knock off so maybe I'll get a real Yamaha one. I think I'll pull the carb and clean it. I've rebuilt plenty of car carbs so I feel comfortable with that.

Yep think i'd not worry about compression at the mo. If your gauge is a screw in type & you kick it hard a few times it should give a good reading or get someone to hold it hard in if its that type with a rubber taper fitting. If it has spark & 'some compression' it should get excited. Is it likely that it's just flooded up. Is the plug getting wet. Sorry, bit of a guessing game without being there.