I'm the fellow that did the Ryobi 31cc glow mod. The WT499 flowed plenty enough fuel to keep the 31cc happy. As a matter of fact, I had to screw the needles quite a ways in to lean it out for 5% castor 0% nitro fuel. I also tried 15% nitro 18%, which requires an even richer setting because of the additional nitro, and the carb kept the engine happy at darn close to 8000rpm. I didn't dare go past that for fear the stamped conrod might blow up in my face.

My rough guess is that the WT499 will feed up to 40cc at normal RPMs no problem. Now whether the venturi size will flow enough air for that big an engine and still maintain good volumetric efficiency to produce optimum power I do not know.