2006 Honda reflex runs out of gas early

[Maddog]

Owned this scoot two years, and burned lots of fuel. Twice now it's run out of gas and the subsequent fill up tells me it's still got over a gallon in the tank, shit I can see fuel in the tank.
It's probably got the typical vacuum feed petcock, but I'm expecting to see some debris on the pick up screen.
Oddly, this scoot never sits, it's my daily driver.
After it "runs out of fuel" I fill it up with 2gal and it runs great! The pisser is it holds 3.2 gal.
I've run 3.1 gal out of it before!
Anyone seen this before? I'll be wrenching on it in the morning, and hope it gets me home tonight.