[aerohead]

I've watched two of the videos. I'm a fan of what he's done.
I'll watch all of them, and try to piece together the particulars.
As I've never owned anything but a 21-inch push-type mower, the title threw me off at first.
Riding mowers are a completely different animal.
One of the qualifiers for my CRX's 52-mpg, was the 12-valve head, and tiny ignition pre-chamber which lit off a rich mixture which lit off an adjoining lean mixture, allowing the car to cruise on it's 'primary' venturi.
You had to bury the throttle pedal to get into the secondary, while simultaneously down-shifting to get onto the cam. A real gutless-wonder!
If he's reading his sparkplug color he'll be able to check his jetting.
The famous 'vapor' carburetors all sacrificed power, speed, and utility on the alter of mpg.
Some guys I've known defeated their Rochester, Holley, and Carter 4-barrel secondaries, happy to loaf around at lower 'performance.'