That was when I learned that if the cover is almost, but not quite, back on, the oil will splatter slightly over everything nearby. Since it was splattering while I was on the highway, it had splashed backward onto the very hot pipe that takes exhaust to the muffler.
Many of you may have related fun learning experiences under your belt, and be aware that motor oil burns. For those of you who don't: motor oil burns. It smells really vile when spread over a hot, dirty pipe and slowly burning off the surface.
I haven't made it home since making the discovery (spent the evening at a girlfriend's house). So until I clean the pipe, oil will continue to slowly burn off the pipe and make a terrible stink.
Luckily the oil was leaking relatively slowly, and so the engine was never badly low on oil... So I got to learn this lesson without having to buy a new motorcycle. Yay!
And that's today's fun lesson! Like most simple irritations, it's also a further illustration of that wise, old axiom: if you swallow a single live toad in the morning, nothing worse is likely to happen to you for the rest of the day.
I'm still not sure I want to swallow live toads to keep this from bugging me next time.