Cornnuts

I just purchased a set of KG 5.5 from my brother. The speakers have been in storage for 2years. One of the horns has no sount coming from it at all. I did the obvious and switched the working horn with bad to eliminate the drivers, but the good horn worked fine in both cabinates. I took the horn apart and noticed some oily stuff in the speaker maganet where the cone slides into, is this normal? The working horn had the same condition but doesn't seem to impeed its performance so my guess it's there by design. Can I get the horn tested? Should I just replace it? Any recomendations for a retrofit horn if it can't be replaced?