From the land of OZ
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"They seem to be shipped with engines that do not have tanks.
It is a pulse unit. The two barbs kind of in line with each other are for the fuel line. You can blow one way in and it comes out the other. Those go to the lower tank and to the engine.
Rather than vacuum, I think it works on crankcase pressure. When the piston comes down, the pressure in the crankcase blows through the rubber tube connecting it to the back of the air cleaner.
Haven't found any instructions, but I assume you put a tee in the short engine tube and run a line down to the hockey puck pump. So it either works on pressure or vacuum or both?
That way you don't have to have a carb with a pump built into it like the China knockoff does if the tank is below the carb.
You will notice there is a sentered bronze filter in the side of the puck. I think that is the vent for the pump diaphragm.
Neat idea for anyone using a rack mount and has the tank down beside the engine to cut the height."
Hope this helps,
ocscully