The reason I recommend the stock Saito carb is two fold.
The gas carbs on the Saito engines do not work the best in the world as far as being easy to adjust.
The Two smaller Saito Gasoline engines, the FG-14 and FG-20 have such a weak pump and no reulator that they almost have a glow fuel carb anyway.
The expensive Walbro WYB carb on the FG-30 & 36 are impossible to get parts for and some of them have been problem childern for the owners as far as the pop off pressure setting goes.
You cannot use a regular Walbro carb on a four stroke. You have to ad a pump diaphragm return spring or else buy a carb that was used on a four stroke in the beginning. One such carb is the little Walbro WT-456.
Here's a link to the Perry pump
http://www3.towerhobbies.com/cgi-bin...&I=LXDG63&P=ML
Here's the Cline Regulator
http://www.billsroom.com/pcfs/
Here's the Iron Bay regulator
http://www.ironbaymodelcompany.com/i...es/Page438.htm