[Gaz64]

Yes, the rear carb is the primary carb, since the primary barrels are closest to the centre of the engine.

The rear carb moves first, (as the primary), then the front carb moves with the interconnecting progressive linkage.

The rear carb should be used for final idle speed. The front carb can be adjusted for near 50% total airflow. Your own personal preference will dictate this choice.

Gary