Hi barber, welcome to Outdoorking.
I suggest you look at this thread:
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=22796&page=1The secret is to remove the pulley and drum drive mechanism in one piece (don't try to take the pulley off the shaft) by undoing the grub screw that holds the drive unit on.
Note that the 430 and 590 models are the same in most respects: the process for dismantling the drum drive is identical.