I think the most dificult part to solve is how to make work a gas carburetor in a 4 strokes engine

first is imposible conect pump direct to crancase fitting. engine and pump stalls.

Some engines has been conected with 2 fitins to carb, passing crankcase preasue into the pump, it is not to good because it stalls wit oil and sometimes heaty damage diaphragm

walbro developed a system, using a small spring in pump diaphragm that letys work only with negative preasure, and it is usually conect to mainfold intake.

I tested thuis system and get bad results, when engine is in idle this system works nice, but when engine is full trotle vacum is not enought to move pump.

In fact we have been contacted for saito fg owners that says engine has problems with carb in this way.





For me the best way to activate pump is the backplate p`reasure usisng a small valvle . I get some problems in ver 3 system just like some engines that passes to mcuh oil shcok the pump with oil.
fianlly we get ver 4 Im proud to say is the best way to use gas carbs in 4 strokes