On the right side front of the case, there are three vertical fins. At their bottom, they are dripping oil onto the right exhaust pipe:
(http://gs500.kicks-ass.org/photos/05/10/30/1733/leak.jpg)
In the left picture, there is a vertical case bolt visible between the exhaust pipe and frame; it usually has a drop of oil hanging on it. Also, the two right side cover bolts that appear forward of the case-saver (in the right picture) usually have a drop of oil hanging from them.
The top of the right-side cover is usually a bit oily. But looking at the very front of the engine, it appears to me to be more shiny below the split in the case (a half-inch below the upper frame mount bolt).
I figure that oil mostly only goes down and back, so the highest, furthest forwards place may be where to look. Since the fins on the front of the engine have oil, I wonder if that means it's probably not the side cover.
It may be easier to pinpoint the leak if you get some degreaser / contact cleaner and clean the front of your engine really well. Then let it sit over night / idle the bike or even take it for a short ride. The dirt will attach to wherever the oil is coming out and form a track leading you back to the leak.
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Looking at my "bench engine" and the one on the project bike, it could either be the case gasket or that bolt could be below spec.
Use some engine cleaner/degreaser to remove all the oil and dirt first. Then spec the bolts up to torque and watch for more leaks.
I can't imagine why the case gasket would be leaking without undue stress.
On my 1997 the timing chain tensioner was leaking like a sieve. It pooled up in front of the starter motor cover.
The odd thing was, it didn't drip anything for over a year and a half. The PO was not one to even check valve clearance, so I imagine that all the bolts have been where they are for the 13 year life of the bike. It would seem odd for a bolt to become insufficiently torqued after years of riding.
The case savers were added last spring, so that's the only thing that's changed. And of course I've had the exhaust and oil cover off.
It drips onto the right tailpipe, even when leaned over to the left on sidestand; so I'm thinking that it's probably not the cam chain tensioner.
I'll try taking it to a car wash and spraying it down with engine cleaner, then rinse. Then run it nice and hot and see what drips where.