I'm installing a 15t tonight and I was wondering if I need to put any grease on the new sprocket.  I haven't really looked at the old sprocket so I don't know if it makes any contact with anything other than the splined drive shaft.  Does it rub the engine case anywhere?

no the chain will lube it just fine.  Nothing special is required..

Cool...Thanks!

I have found that a little grease on the splines makes it slide on a little easier.