The WT-456-1 arrived, and it's new in the box. Clearly never been used. For those interested in an Ebaywalbro sellerwho is responsive, his Ebay name is captneversail. Give him a try.

Besides getting my Saito conversion running correctly, another goal has been to understand (IN DETAIL) what Walbro did to their existing designsto marketthe intake-pulse-only carbs for 4 strokes. This 98-3226 spring is obviously a design mod rather than a clean sheet 4 stroke design.That opens the potential for budget conscious modellers to convert existing carbs to 4 stroke. The carb is $37. The spring is47 cents. Duh. It looks like the only difference is the diaphragm cover, and it only differs by the machining of the little flat bottom counterbore (see photo). The 4 stroke cover on the parts listis obsolete, but there's a replacement for $2.50. To save time or money, one could machine the old cover. The counterboreis .380" diameter, and it's .045" deep as measured from the cover mounting surface. (not the gasket ridge, but the surface just outside of that). I think this could be done on a drill press if one clamps everything tightly. Just grind the angle off the tip of a SHORT3/8 drill. It should be short to keep the drill from chattering. Grind a clearance angle behind the two cutting edges on the drill.

In the two photos below, one is a non spring-assisted 2 stroke carb, and the other is a known 4-stroke carb, the WT-456. This was used on RyobiAC trimmers. This isa line of 4 stroke products called "Air Clean" to address mounting critisizm from the greenies about 2 stroke pollution. They even made their engine designs open source forothers to copy,ostensibly toforestall government regulation. I'm showing both carbsto illustrate where the parts are common, and where they differ. And also to show how the WT-456 4 stroke spring assembles. Maybe there are other differences, but I can't find them if they exist. I add that as a caveat to innoculate myself against anyone yelling at me for an incomplete analysis.