Yesterday I tore my 400 down and gave it a good cleaning. I took some aluminum wheel acid wash to all of my aluminum parts. My engine looks brand new, it got all the baked on dirt/mud off of the cooling fins. My hubs look brand new, it really cleaned up my rear shock from a dull brownish color to a bright aluminum color. A little got onto my swing arm and since it is coated, it left some discolored spots, but a little elbow grease I am sure will take care of that. Just thought I would pass this info along. I just wish I would have taken before and after pictures.