Chainsaw Repair

It does sound like the vent but also does this saw use a primer bulb? If so are you sure you have all your lines going where they should?  The line with the filter should go directly to the carb lower rh side and the primer bulb should pull fuel through this line into the carb out the lh side through the bulb and back into the tank. The return line from the bulb does not have to be long enough to get down into the fuel just into the tank...