I just got some 550 controls last night. I needed to clean the cobwebs out and check the extent of the rust, so disassembly was my only choice. I was surprised at how easy it actually was. Of course I swept the floor first, and put a towel on the bench to catch the little parts. Good thing ,cause all the parts are small, and I'm very good at dropping stuff. I didn't take the starter button housing apart because WD-40 made it work well. reassembly was tedious, but grease, never-seize, and plenty of time did the trick, I won't hesitate to clean another set. next step will be the soda blaster to see if I can get an even finish/color for clearcoating.
