Your overlooking something, this is a simple circuit.
Black hose pumps air through the check valve into the remote tank, thus pressurizing the remote tank, and pushes oil to the reserve reservoir through the black hose with blue stripe.
Note: Oil will NOT flow to the reserve reservoir, from the remote oil tank, unless the vent cap is open on the reserve reservoir.
Try swapping the 3-way check valve ( fitting only has hoses on TWO of its three ends) at the reserve reservoir, with one from your other motor. Check valve is located below the reserve reservoir, right above the shift cable.