Originally Posted by Ridin' Green
They are the metal (in some instances they are plastic) shrouds that cover the engine's upper end (the end where the air intake screen is on a horizontal shaft engine). They are held on by a few small bolts. Just remove them, and anything else being held to the shroud by the bolts, and clean the engine cooling fins real well once or twice a year.
It's the large black cover in this link-
What brand of WB is in the pic at your link? I don't recall ever seeing a black deck under a yellow deck cover. Hustler?