Gosh, I wish I had found this website sooner!!
I have a 2002 DR650SE. It hadn't been ridden much by the previous owners, thats why it's only got 23000km on the clock now. I bought it 2 years ago with 13000km on the clock! Anyway, I noticed oil on the right side crank case cover.
I washed the bike and took it for a short ride, to see where the oil was coming from. It seemed to be from the back of the cylinder base gasket. So I bought all the gaskets and copper washers that would need to be replaced, to get to the cylinder base gasket. Imagine my disappointment when I stripped everything and found that the little gasket under the cam chain tensioner had a crack in the top half.
The oil was running down the left side of the CCT and onto the crank case, just below it, right at the join of the cylinder barrel and the crank case. I didn't notice this, as I only ever looked from the right side of the engine.
I took the opportunity to get to the neutral light switch and put some service grade locktite on the little screws. The service grade locktite allows you to unscrew the screws, in case you ever need to.
My cousin in Townsville Australia, sent me a link to this site. He knew about my bike's oil leak and found a thread where the chap had sprinkled talc powder on the engine, to show more easily where the oil was coming from.
Well the experience gave me an opportunity to check inside the engine and see how the bore and valves were doing. Still only has the criss-cross from the honing in it. I'll feel a lot more confident when we ride from Pietermaritzburg, up to Maputo and back, in June :-)