How do i get the hub off my homelite st185 to fix my pull chord?

I assume you are talking about the clutch shell. This has a square receptacle on the small end that the square end of the drive cable to the cutter head fits into. The drive cable will pull out of the clutch shell. Insert a #25 (might be a different size) torx driver through the square hole where the drive cable came out. Engage a screw and turn counterclockwise. The clutch shell should lift off.

To remove the centrifugal clutch assembly, take out the spark plug, rotate the engine so that the piston is down, and fill the cylinder with a small cord to keep the piston from coming all the way to the top of the cylinder. Then you can screw the clutch assembly (counterclockwise) off the end of the engine's output shaft.