My mistake, that was a typo. I meant to say my old VK-30 bore measures precisely as 2-1/4". I just went and measured it again and can see you are right. But I would have to say it is just barely 2-5/16". It is actually a smidgen smaller according to my calipers - sort of in between 2-1/4" and 2-5/16".
Just to confuse things, I was just looking at some original LAV-40 engines on a reputable American site that sells Tecumseh engines, and one engine block clearly had the intake port at the bottom, but the other had the intake port at the top. Also they both had different styles of fuel tanks. It seems like there were a number of different models of the LAV-40.
Here is a LAV40-50392E with intake port at bottom.
