I picked up a new K&B .20 on Craigslist today and in the box was what looks like a 4-stroke carb. It looks to be about right for a .40 size 2 cycle. I have several Saitos and they are my only experience with 4-strokes. This one does not match any of them - smallest I have is a fa-72. And none of them have the recess this one has in the machined area for the bolt holes. Can anyone help identify this?