750 Eddy Carb issues

Make sure the doggone secondaries close on the stop, and not on linkage interference.Back off the secondary throttle stop,and make sure that the two air valves both hit the throttle-bores simultaneously. Then reset the stop just enough to prevent sticking. Then make sure the flyweights in the D snap back onto their stops. After you get that done,Check/adjust your T-port sync,
AJ's guide to Transfer Port Synchronization

Hyup on the vacuum thing.
Finally,install a vacuum gauge on the manifold.With the engine idling, loosen one of the metering-rod cover-screws and flip the cover to the side a bit then retighten the screw,enough that it cannot come loose and fall into the engine. Then observe that the piston remains down, at idle.Then slow the engine rpm and continue to watch the piston as the vacuum drops. If/when the piston starts to dance,increase the idle speed about 50 rpm,and observe the vacuum reading. That will be your minimum vacuum required for the springs that are under the piston. If your engine requires more than 700/650 rpm to achieve that, then you will need different springs.