This might be helpful, might not, don't know the Dellorto setup. In the Mikuni 33 mm. 4-stroke flat slide pumpers a dowel on the bell crank holds the AP actuator back, and when the throttle is cracked the dowel releases a spring that pushes the actuator down.
Spent hours at the bench trying to figure out why the AP nozzles wouldn't spray. They sprayed just fine if I pushed the rod down hard and fast by hand. Finally the obvious got through my thick head--the carbs were from the 1980s, the springs were under constant tension and had weakened after only 40 years or so, and the weak springs pushed the rods down too slowly; pressure was lost before fuel got to the nozzles.
And although Mikuni America continues to sell the similar TM33/8012, they don't see fit to import the spring. I was about to order from Mikuni Topham in Germany when it struck me that I might as well try shortening the spring--it was no good anyway as is. Took 1/4" off and the nozzles sprayed like they're supposed to do.
