After removing the balls that seal the idle passages, you need to drill the primary and secondary passages with a #40 six inch clean out drill bit as shown in the diagram. The idle passage #1 will be up through the bottom two passages. The secondary passage #2 will be through the front of the carburetor. The drill bit can be purchased from Robert's Carburetor Repair. The part number is #RC1408. To learn more about rebuilding Duplex Carburetors you can also purchase the video "How to Rebuild Duplex Series Carburetors" from Robert's Carburetor Repair.