Yeah, carburetor. I'm not one to throw working hardware out. The mower before this one was blowing signficant oil byproducts out the exhaust and was clearly in need of an overhaul, something I'm not quite set up to do (I've done old VW Beetles, they're not much different), but don't have a good way to turn the crankshaft and all.. nor the time, and bought a replacement four or five years ago, just before electrics moved off of, "It's a high priced curiosity" status. This particular one gets its oil changes on time and all, but some time last year the air filter body broke a piece of plastic, so the cover wouldn't stay on over the air filter. Duct tape fixed that, but I didn't like the solution.
Local shop could and did order a new air filter body. So, yesterday, hauled out the tool box, unbolted the air filter body.. and then discovered that not only did the air filter casing fall off, so did everything else, right up to the engine intake port. That included this minuscule little carb. Cute thing: Has the float tank on the bottom, jets, and all that. But had a devil of a time figuring out which of several gaskets sealing the carb to the engine, the carb to this plastic thing with controls for the throttle body intake, and the throttle body intake to the air filter body went where. Got it all back together again, crossed my fingers, and, after a couple of pulls, the engine started. Slightly odd, though: the engine kept on mildly speeding up and down on its own. Then happened to look on the garage floor and there, by gum, was another gasket. Stopped the mower, turned off the gas valve, disassembled it all, put the found gasket back where it belonged, reassembled everything, and, this time, it started on the first try and ran steady.
It's got a few more years to go. Changing oil and all on a good schedule makes these things last a looonnngg time.