It almost seems like everytime the workers at Walbro come back after coffee break, the forgot what they were doing and start a new model. There are more Walbro model numbers than Carter had little pills?
The WT-456 is a carb like you are referring to. It comes from the old original Ryobi 26cc four stroke. It is a butterfly carb with both a high and low needle and it has the fuel pump spring you mention.
The spring itself is part number Walbro 98-3225-7. You might could try this spring in other carbs?
Walbro carbs with an accelerator pump and the high speed nozzle check valve would also be nice like is on this Walbro WT-456.
The Saito 150 most likely would not need a ''28'' size carb like a 25cc two stroke engine because the Saito is a four stroke?Â* I say this because the WT-456 is small (#16) when you start looking at it. But at least give it a try?
The Honda GX engines all have barrel type Walbros which is no big deal but none of them have high speed needles which is bad.
The Saito FG-36 gas engine has a Walbro WYD carb which is a barrel type with the pump and regulator 90 degrees apart whereas most WY barrel type carbs have the regulator mounted underneath the pump.
The WYD has a pretty good sized venturi and might be too big for a 150? I have no clue as to the carb on the new Saito FG-30. It appears to be a WY style but that's all I know.
There is little information available on the Walbro WYD-1-1 and WYD-2-1 carbs.
The barrel spring on the Walbro WYD carb works backwards compared with the barrel spring in a model airplane engine carb. The spring is on the front of the barrel and pushes the barrel towards the carb body rather than away from it. The low speed mixture screw is in the center of the barrel in a Walbro WYD just like on a model airplane engine carb. But the spring tries to close the barrel and not open it like on a model airplane carb. To choke this type carb, close the barrel and pull out on the throttle lever which will pull the low speed needle out of the barrel to the high speed position effectively allowing the engine to suck a lot of fuel through the carb.Â* The Walbro guy that designed this carb is a model builder and generally seems to like war birds.