If the lower lockout is preventing the secondaries from opening , 2 things will cause this. First if the choke element (spring) is malfunctioning it will not heat up and rotate the lockout away from the secondaries. The other thing that will
cause this is if the pin on the back of the choke housing has worn or gotten loose where it attaches to the lever arm.
Is your choke electric or hot air on this carb? If it is hot air, check the tube going to the choke housing to make sure it is not rusted out or blocked. If it is electric, make sure that there is no gasket between the choke and the housing and
that with 12volts to it, it heats up and moves the element (spring looking piece). Now if the pin is loose on the lever or just worn down some, you can cut a small piece of vacuum hose and slip it over the pin , just verify that when rotating the choke in the housing (to adjust it) that it will disengage the lockout lever when it is moved to simulate the choke in the full open position.
Paul