I have a 1985 vf500c that i recently purchased. It had no leaks of any kind.I took bike into shop and had new sprockets and chain installed.When i got home from shop(which was in a different city), I noticed it was leaking oil. Can't spot exactly from where but looks like from front sprocket area. I am taking bike back to shop but wanted a heads up on what source could be incase they try to skirt the blame.  

Possibly someone at the shop used a screwdriver or pry bar to get the countershaft sprocket off (which, after 23 years, might have seemed like a good idea).  The prying would have put force against the oil seal and, presto--oil leaking.  Good luck.