Small Engines (Lawn Mowers, etc.): Echo hedge trimmer, echo hedge trimmer, carburetor work

Question
Marc , I have a Echo hedge trimmer that is giving me problems. I looks just like a small chain saw engine. My problems started one day when I wanted to use it . The trimmer was hard to start and would only run a idle or part throttle , If I tried to increase to engine speed it would die. After using it (for what little it would do ) I took apart the carburetor and cleaned it . Still I have the same problem , after fooling with it  somemore it seems to be worse to the point were it just won't run. I have tried choke open , part open and wide open and still it won't run . The one thing I find is it will at lease start for a second or two when the choke is just about all the way closed but won't run at all with the choke open. What makes the diaphram in the carburetor work back and forth to open the needle valve? Is it the suction created from the piston? I looked at the diaphram and I don't see any holes but aleast to me I think it is a fuel problem. I have the carburetor apart and soaking in cleaner and plan to leave it there over night , maybe something is stuck in it? any thoughts?  

Answer
Sorry for the delay....there must have been some issue with me not being notified.  If you are sure the carb is clean and the mixture screws are started at 1 1/2 turns out from lightly seated, the problem may be related to the impulse hose (or passage) from the crankcase.  The pulses from this hose operate the fuel pump diaphram in the carb.  Another problem could be a plugged fuel tank vent.  Hope this helps.