My old 1972 carburetor has gotten tired, so I swapped a 1980 A14 carburetor on the old A12. Runs quite well, but the secondaries don't open.

Before I put it on, I made sure they opened when I turned the throttle shaft. Then I drove it around, it runs great at 100kph but takes some time getting there. So i stopped it and looked down the carb. The secondaries don't open. I flipped up the weighted flap, and can see the secondary butterfly doesn't open.

Any ideas?

Being a later model carb, does it now have vacuum operated secondary instead of a manual linkage? Quite often the factories used the same major parts for the carb throttle plate body etc and just fitted an external vacuum diaphragm actuator. If the vacuum gubbins wasn't supplied with the carb then could be the issue?

Thanks for the idea, it was something blocking the linkage. The A12 manifold has a boss that was stopping the throttle linkage. Just a little mod fixed it.

It now runs nice and smooth and with plenty of power.

Cable tie the weighted flap in the open position, and consider it a mechanical secondary!