String Trimmers

Bought a 224L string trimmer today at Lowe's. Gassed it, read manual and started using it. Worked magnificently for about 20 minutes, then began stalling repeatedly. Also smoked a bit. After restarting it about 20 times and having it stall the moment the trim head touched anything, it got to where it would run about 3 seconds then stop, without the trim head coming into contact with a single blade of grass. Thinking it was overheating (air temp was 54 degrees) I let it rest for about 15 min, then it worked okay for a very short time, then began stalling again after only a few seconds. It starts easily. It would not stall if I kept my finger off the throttle. I paid $350 for this thing, it had better work for more than 20 minutes.