I've cleaned my 89 seats a few times with no problem. I'd be willing to bet
that there is a bunch of dirt in the seat that just comes to the surface
the more you scrub. If it really looks that bad, you have nothing to lose
by using a steam cleaner. I've seen three late model westys cleaned to near
new condition with a steam cleaner (including mine). I'd give it a try. I
think you'll be happy.

-Phil
89 Westy