If you're talking about the
sump strainer - there's good argument to splash-the-cash and fit the aftermarket version from MikesXS / Heiden tuning as the originals are reported to tear the mesh away from part of the plate (leaving a nice big hole!)
http://www.mikesxs.net/product/15-6500.htmlIf you're talking the screen filter that sits in the
RHS casing, and want to spend more pennies, MikesXS / Heiden sell a paper filter (Honda motorcycle part) and an adaptor so it'll fit the XS.
http://www.mikesxs.net/product/15-6504.htmlThis means a detergent oil actually has somewhere to collect the nastiness as opposed to letting circulate till the next oil change.
http://www.xs650.biz/p/28/1423/home Heiden in Holland (Europe outlet for Mikes XS)
http://www.mikesxs.net/ Mikes XS in USA
For that don't know, the XS650 (which came out around 1968) runs two separate gauzes - great for catching solid lumps, but that's about it