The Zama can actually be just a good as the Walbro.

It's just that people in the past had a harder time cross referencing the Zama.

A lot of this has to do with the little number cast into the venturi of the Walbro ie "20", "28" which helped people readily identify sizes of carbs.

Whatever you do with your carb, you are going to need both a high speed and a low speed adjustable needle valve to use the engine on an airplane.

With the Ryobi engine, a choke is a good idea but not so important on piston ported engines mounted without a cowl.

Enjoy,

Jim