Hi folks! I'm a relatively new RZT-S 42 owner; bought it last year and now have a whopping 26 hours on the clock!
I have a sludgy black buildup at the rear of the mower. Last year, I figured it was just soot. This year, I see it's sludgy and pasty. It looks like leaky valve covers to me:
For more pictures, see:
http://imgur.com/a/BAUlR
Is this normal on these mowers? Geez, it's still new...