Hi David
Is that the pipe that goes from the petcock into a T piece and then the other 2 pipes each go to a brass pipe on top of each carb? If so it is part of the system that operates the vacuum petcock. All these pipes should be clear. There is nothing inside any of them.
When the petcock is set to ON or RES there is a diaphragm that prevents petrol flowing into the carbs. When the engine is turned over the carbs suck air through these popes which in turn pull the diaphragm and opens the petcock to allow the fuel to flow. Ant leak or obstruction could serious disrupt petrol flow and thus cause running issues. You must remove the obstruction or replace the pipe. I have replaced mine with clear PVC tubing.
A way to test if this is your problem is to switch the petcock to PRI. This is prime and bypasses the diaphragm circuit allowing free flow of fuel.
