Nikki Carburetor Secondary Slow Transfer
For higher speeds the Nikki carburetor includes a secondary system to supply extra fuel when needed. This is done by used two methods. The Nikki includes a secondary diaphragm which is controlled by vacuum. As the engine speed increases the vacuum from the intake causes the diaphragm to open the throttle valve.
A lockout is used on the secondary to keep the secondary from opening too soon.
The secondary vacuum port is smaller than the primary to help control the opening timing and to allow faster closing of the secondaries when the accelerator is released.