screeching

Mini bike screeching im not that smart on mini bikes but I know a little about them I wanted to know if anyone could help me with this problem it has happend before but we made some changes and it was gone for a few days but it started after riding for a while so I wanted to know if anyone could...

I am new to the MB world and though I understand the concepts of the centrifugal (sp?) clutch, the one on my DB30 is having a problem. When the mtor is at idle, it screeches and kills the motor. I have pulled it apart and it appears to be clean. What is the most common cause of this...