Any one know for sure if the fuel pump portion of the carb. pumps both on negative and positive crankcase pulses?

Built in check valves, one way pump. If it was a bi-directional pump it would pull fuel out after putting it in.

You can use a spring in the pump and use an external pulse to the intake. AV8TOR can tell you better.

It sucks in the fuel on one pulse and pumps it out on the other.

Thanks TKG that is what I was looking for.

BINGO !! This is exactly what it does. It's a very cool simple little device. Only one check valve is open at a time, and they volley back and forth duing positive and negative pulses.....that's how it does what tkg said.

See end of page 5 and beginning of page 6 for pump sequence description:
http://wind-drifter.com/technical/Wa...viceManual.pdf

You could cut the pumping section out of a pumper carb...and use it in line to make sure fuel does not run back to tank. Capt,n