I have an older Poulan trimmer that has developed on odd issue. After use it will continue to siphon fuel out of the tank, out the carb, and onto my garage floor. After about a week or so it will drain the entire tank. I store it with the choke wide open.
Find the part number on the carb and go to a OPE dealer or order off the internet a new carb kit for it. You will have to take it apart, clean it and then install the new parts that come with the kit. Go to you tube and search for videos on how to reapair trimmer carbs. There are some very good ones and some fair ones. Keep watching until you have a decent understanding of it. Another option is to just buy a new carb from the same place that supplies parts. They are not much more than a good kit. Last option, toss the poulan and buy a new one.