I have a tory-bilt 4cycle string trimmer,the problem I'm having is the trimmer will start and run idle,but when I go to squeeze the trigger it cuts off but will start again but cuts off every time the trigger is pulled.so can someone please help.

Its most likely a carb adjustment or fuel filter is clogged in the tank.

Hears some basic on carb adjustments if necessary.
YouTube - how to fix 2 stroke weedeaters (http://www.youtube.com/watch?v=y1xsHICIBqk&feature=related)