Husqvarna 555 Carb test, what is this hole?

[Broke Again]

Trying to pressure test this Zama el49. I'm getting bubbles out of this hole on the back face. It goes through a weird hole in the intake underneath the main boot.

What is it for? Is there supposed to be air coming out when pressure testing? I cant find any explanation for it.

 

[Bob Hedgecutter]

Guessing it is the impulse channel. Crankcase pulse works the carb diaphragm to pump fuel from tank through carb.

As it is a 5 series saw I have little or nothing to do with........ See page 35 in this PDF

https://www.hlsproparts.com/v/vspfiles/downloadables/WM_555-556-560XP-560XP-562XP-562XPG-2018_1152656-26.pdf