I have a 530 but I've never had to remove the assembly. One thing I'd be curious to know...The stitch length control on mine has never gone all the way up or down. It does reverse fine, but the lever has never moved all the way up or down. I'm wondering if it should be able to. I've oiled it and there's no gunk, it just seems that it has a limited range of motion. So, someone has either tinkered with it or this is simply how this model operates?