I took a real close look at the Toro trimmer at Home Depot the last few times I went there, and they sure look interesting. I would have guessed Kioritz as the OEM except the spark plug is straight like small Zenoahs, not angled like all the baby Kioritz I've seen.

Anyway, the back of the engine has some kind of mechanism on the cylinder. I can't quite make out what it is, but it looks like some sort of emission control device. EGR maybe.

If it ever goes on sale, I'll definitely pick one up to play with. It seems like every monkey and his uncle makes a 25.4cc twin ring, twin BB, twin counterbalance weedie engine. I'm smitten by the two I got.