Chainsaw Repair

I'm working on my dad's Cs-520 and the carburetor isn't pulling fuel into it. I just rebuilt it, the tank vent brand new and works perfectly. The fuel line is not clogged, I pulled a vacuum on it with a syringe and it filled up with fuel.  The impulse hole is working fine. When I have the carb hooked up I can pull that cord 10 + times and when I open back up the carb it's bone dry. I'm starting to go especially crazy over this because it's the third machine in a row I've worked on that's done the same thing. 2 carb rebuilds and one brand new carb. I think I must be doing something wrong, but I rebuild carbs usually multiple times a week and never had this problem before. Does anyone have any ideas? I've got to take a break before I drive myself more crazy and figured I'd try and get a second opinion.

Man I hope so. I'll look at it next week.