Air lever on the left operates the carburetor shuttle through the control bell-crank and the petrol control lever on the right operates the regulator plunger.
The regulator plunger contains the regulator needle, allowing for fine adjustment of petrol flow through the regulator.
The petrol passes through a fine #30 mesh filter at the bottom of the body. The tapered needle position determines the amount of petrol that will be supplied from the selected petrol tank, through the output connection pipe, to the carburetor.