The pull string broke on my Troy Built Weedeater Model #TB20CS I have it apart built cannot get the red housing off to grt to the string assist mechanism. A silver metal cam is preventing me from doing the job

Hi,
I assume you are referring to the clutch drum, despite spelling. A torx driver (T-20 or T-25) fits down where the flexshaft normally goes and the screw in there loosens counter-clockwise. Then the clutch has to come off (it has an arrow on it.)
Peace,
Clarke