Find a used Kohler Carter #30 carb and throw a rebuilt kit in it. Trust me you will not regret it.
Walbro carbs are complete garbage especially on a kohler engine. Very hard to clean and they do not idle down very well on a kohler. They have a tendency to run rich at WOT and Lean at Idle. It's impossible to get a Kohler to idle down below 1200 rpm with a Walbro carb and still run ok at WOT.
The 1st thing I did when I got my Cub 149 was get rid of the Walbro carb that was on it. The difference in performance and reliability alone is worth it. It ran ALOT smoother and seemed to have quite a bit more low end torque. And it would idle down nice and low.
Before with the Walbro carb it was sputtering and coughed every time I ran over a bump in the yard. It would bog down and almost stall if you jammed the hydro leaver forward from a dead stop. It did the same thing after I cleaned and rebuilt it, even after setting the float at different levels. With the #30 Carter on it there is no more sputtering or cutting out and it has Alot more grunt.
I've cleaned and rebuilt and tuned alot of Walbro carbs over the years. Tecumsehs seem to run ok with them but the cast iron Kohlers don't like them at all. There not a very well designed carb in the 1st place, especially the very restricted idle circuits.