The best of the small single-cylinder engines I've had didn't have a
carb as such, was a B&S with a Pulsa-jet. *Crankcase pressure pulses
pumped gas into an elevated well in the tank, then the venturi sucked
it in. *Only real wear part was the pumping diaphram and it never went
bad. So no needle or float to mess with and only a mixture screw. No
shutoff valve needed, either. Always seemed to take off after a couple
of pulls no matter how many months it sat. Was discontinued, of
course.

I've got two of those motors, and three carbs between them. The new
gas still manages to gum them up solid.
--Glenn Lyford