how can I repair my ryobi trimmer rct2800cb ?

I have a ryobi trimmer rct2800 trimmer fitted with a walbro carburetta.
When I try to start it, the carburetta usually floods, and the primer button seem to build up pressure in the tank, and the carburetta ouses fuel until I open the fuel cap, then it slow up.
the carburetta floods easily.
It is difficult to start, and if I manage to start it, it will run for a while untill I switch it off , then it wont start at all.
Some times it will only run for a few seconds.
What do you recommend.to solve the problem.