Perhaps an explanation of how the pump sucks (sic) and pushes might help a little:
The inlet port from the tank needs to be well under the oil level in order to suck at all. That's the one toward the back of the pump: it technically needs hydrostatic head taller than the top of the pump in order to feed it fully (that's why the oil tank is so high on the bike's frame). So, set the pump in the SumpThing's pan and fill it way up to drown as much of the pump as possible. That's one thing I had to do when I put on the SumpThing.
Rotate it the same way the crankshaft turns (to the right in your picture above). Rotating it backward will cavitate the suction side and make it [re]lose prime.
The other thing I had to do, because the pump is sitting flat on its suction screen for the scavenge side, was to lay a thin wrench (6mm in my case) under the suction side of the pump to tilt it (a little bit toward you in the SumpThing picture above) so the oil was easy to draw in. Then I also propped open the suction discharge port (the one most forward) with a mechanic's wire (thin steel wire) to more easily let the meager suction of slow-speed turning not have to fight the spring in the check valve. That then loaded up the suction side, which then improved the suction of the pressure side, and finally filled both sides of the pump.
Yeah, the Sump Thing is one of those gizmos made to sell, but not necessarily made to be easy to install. It does have nice machine work on it, though!
