On the intake manifolds, each one has a brass pipe. Two face downward, and two face upward. The two facing upward get the two vacuum hoses to the suction valve switch above the motor. The two facing downward are capped off with thick, rubber caps.
The vacuum petcock has a vacuum line that goes to the #4 carb body near the engine side.
Each carb has a bowl vent. The ones for 1 and 2 are T-fitted together into one hose. The ones for 3 and 4 go to another T to another hose. Those two bowl vent hoses just go up above the airbox and dead-end there, open to the atmosphere.
Each carb also has a drain hose at the bottom of the bowl.
The air suction switch has a large hose that goes to the airbox, and two slightly smaller hoses which go to the valve cover.
