What is this hose for?

[JStrunk]

I have a Sachs Dolmar 120 Super that I am working on. It originally had a primer bulb on the tank handle but was long gone since I have had it. It has had a bolt, nut, and an o ring in its place. I have a 120SI handle that I want to put on it but have questions about the primer bulb operation on the old handle. Did the bulb shoot fuel into the plastic intake elbow through the 90 degree barb prior to the carb? Currently on my saw the 90 degree barb on the intake is connected to a rubber hose that goes into the fuel tank but isn't connected to anything (nice!). The intake on my saw is 6b in the second picture. From looking at the parts diagram it seems that the carb has a separate pickup in the fuel tank. That seems weird to me...I thought the bulb was used to pressurize the fuel line to the carb. But I can't think of any other way it would work since there are two fuel lines coming out of the tank and one vent.

So if I change to the 120SI handle I think that I will block off the barb on the intake elbow since there is no longer a primer bulb and I only have one fuel line coming out of the tank and one vent. Does that sound right? It starts and runs fine without the primer. Thanks!

 

[pioneerguy600]

Its been a while since I messed with my 120S but if I remember correctly there is a one way valve in the Y connecter, when the primer bulb is pushed in the valve shuts and fuel is pushed up to the carb, when released the bulb springs back into shape drawing fuel up from the tank, push the bulb and that shot of gas goes to the carb. Repeat as often as necessary to prime the carb.
If you run the si carb you will not need the primer so you could block off the Y connector branch to the primer.
Pioneerguy600