Because of this thread I re-tried a Perry pump carb and a Perry VP 20 pump on my Fox .74, I have tried this with the crankcase driven pump also, both will supply fuel to about 3/4ths throttle then the engine goes lean and if I'm lucky just quits, Without the pump and placing a piece of wood under the tank to make it too high the carb will supply adequate without the pump. I tried 3 VP 20s and no joy, they are back in their drawer where they're perfectly suited. The pump carb is 9.5mm. I don't see why the carbs would dissolve in gasoline when they make a gasoline pump called the VP 22 out of the same stuff.