The theory behind that economizer linkage is allowing the engine to achieve full advance timing without having to open the carb butterfly fully.
Adjusting this thing is easier with an assistant, one person just doesn’t have enough hand. In any event, spin the prop so the engine can be shifted into forward gear, so that the throttle can be advance fully. Hopefully the throttle cable is still attached to the engine, go ahead and advance the throttle fully if it is. Otherwise, you will need an assistant to move the throttle to WOT position by pushing the throttle cable pin to its WOT stop.
I believe your carburetor has a roll pin on the throttle shaft that will butt up against the carb casting when the butterfly is fully open, let me know if this is not the case.
So, check your economizer adjustment by looking at the butterfly shaft roll pin while the throttle is in WOT position. Is the roll pin up against the casting stop? If so, the economizer is adjusted properly. If there is a large gap between the roll pin and the casting stop, then the carb butterfly is not opening fully. With the throttle control in WOT position, simply loosen the brass barrel screw, then push the economizer rod forward until the butterfly is opened fully and retighten the barrel screw.
One final note. Be sure not to "preload" the carb butterfly jamming it hard against the body stop, this will put pressure/wear on the butterfly shaft/carb body causing premature wear.
