Today, in honor of the Dakar rest-day, I did some work on my 450. First, I've had oil blowing out the vent on the transmission side. After ruling everything else out, I came to suspect the kick start idler gear. Sure enough:
The old one:
You can see that the inner bushing has shifited, blocking the oil passages.
Here's the new one:
Then, using Ned's write up in this very thread, I replaced the head gasket due a suspicion that was what was causing my coolant to spew out, even when the engine was not over-heating. Here's what the inside of the head looked like:
And the valves:
Some weird crystalization there, especially right near the spark plug hole.
Not sure what to make of that.