Gah. This is totally ass backwards.
I took the tank off and took the air boxes off. I rigged up a gas can on the passenger foot rest.
I fired it up just to check the slide operation, which appeared to be working correctly.
Back it out of shop and go for a ride. Runs great.
Back to shop, put air boxes back on, go for ride. Runs like ****.
Back to shop, take air boxes back off, go for ride, runs great.
Jetting in the new carbs? I'm getting so frustrated with the whole thing.