I have the Echo 1600 series bush trimmers. When I go to start them, they will fire but not start. It lets out white smoke when it tries to start. The fuel lines aren't plugged up. We tried to adjust the carborator but that did not work. It seems as if it just burns the gas that is in it but it does not pull in more. The spark plugs are also in good shape. I was wondering if this have ever happened to anyone else or if anyone else may have a solution on how to fix the problem. Thanks for your help. I may have to just take them somewhere else to get them fixed, but I would like to fix them myself since I plan on doing this kind of work as a living.