I just had my featherlite weedeater serviced. It ran like a champ the first time I used it. The second time, after running it for about 10 minutes, it started to smoke slightly from the head which holds the string. I immediately turned it off and noticed black oil (at least that's what it appeared to be) coming from the area that holds the head onto the weedeater. I let it cool off and used it again. The third time I used it the head will not spin when I pull the trigger. It runs very, very slowly. Anyone know what needs done to repair it?