Turns out that the Honda EU gensets are very picky on maintenance. Ours ran fine at the race in October when we shut it off, but wouldn't run during an ice storm 2 weeks ago. We finally had time to look at it. It kept backfiring through the intake, so we took it all apart, removed the valve cover, and found the intake rocker just floating free and the intake valve stuck half open. The oil (1-year old, probably 1000 hours or longer) varnished on the stem, so we had to get creative with chemicals to clean all that up. It runs just fine now after adding more chemicals for a flush, and a new change of oil. Also, in the manual it says to set the valve lash every 300 hours or so (surprise!). Getting to the valve cover is a PITA, but once we fixed the sticking valves, the lash was way, way out. So we put it back where it should be (006 intake, 008 exhaust). Our old Craftsman unit from 1996 is now running, it's been sitting since we bought the EU 4 years ago. Fixed the recoil starter, blew out the carburetor, cleaned all the oil sludge out of the fairing, tightened several loose screws, valve lash was stable at 007, and now it runs again. Just because generators run when you turn them off, doesn't mean they'll run the next time you need them, be it a month later or years later.