Originally Posted by
ranoobu
I also have black stuff on the chains and sprockets.. is this grease? Is it suppose to be there?
If it's on the teeth and sprockets, no it's not, it's grime from the chain. The previous rider probably used WD-40 or something like that to lubricate the chain. Bad idea, that stuff picks up dirt and all kinds of grime. If the chain is really bad, you might want to just replace it, since it'll continue to transfer that junk onto the sprocket and rear derailer, which will mess up the perfomance of the bike.
Not to mention, the grime on the chain tends to solidify a bit over time, which makes the chain less flexible.