Went on a run with a guy with an 05 mostly stock XR650R this weekend. We were doing some light riding on the street on the way to the trail and stopped for gas, when he shut the bike off to get the fuel coolant was spewing everywhere. Luckily there was a bike shop about 1/4 mile down the road and we brought it there for them to check out. They told us it was fairly common and he added some coolant and we went on our merry way with no more problems. We ran all day with no more overheating. It was very weird and sporatic. Anyway, that just happened this weekend and he says the bike is fine!
On a side note, this somewhat justified my reasoning on wanting an air cooled bike for simplicity reasons, one less thing to worry about!
But that spewed coolant still kept that hot motor a lot cooler than an air cooled would have been.