ORIGINAL: hchytd
I did spray it and the bearings with WD-40 though.
If you want to clean the bearings, remove the shields/seals and blast them out with something like motor cleaner or automotive brake parts cleaner(beware, they both have strong fumes and aren't good to get on skin). After blasting them thoroughly from both sides, allow them to dry and either pack them with grease or oil them, then put the seals back in.
RPM makes a jig to help cleaning.
http://www.rpmrcproducts.com/product...ls.htm#blaster