Riding up to the burger joint, about 20 miles on a trail. Eat, leave, it's dark out 54 degrees in the Black Hills of South Dakota. Dave's riding a '04 WR450, I'm on a '06 WR450. We head back on a different part of the trail we've only been up and not down. Needless to say we miss our exit point and get lost. It's 9:15, we're not doing bad. About half tank of fuel in his - I've got the IMS - I'm doing good. 500 yards down the trail a rock wacks his shin and pulls his body off the bike and he goes down the lowside of the hill - hanging on the bars the whole way down. I come around the corner to see a WR450 running upside down ontop of dave. I leave mine running for the light, hop off help pull the bike up. He's about half fugged up but still is able to ride. Meanwhile my header is CHERRY RED. I kill the bike and radiator fluid is just flying out the overflow......This is about the time I noticed his radiator is totally screwed, and leaking bad. Great, I'm thinking we're screwed. Dave had confidence, I didn't. We both run MX4T Mobil Synthetic oil. So we fire them up, too dark to walk, and no moon out yet. Head down the trail and hit a fire road. Listened for a nearby road we thought we were by and sure enough we heard a vehicle. So about 3 miles of fire road and it dumps us off onto the main highway. We got into Nemo, made a phone call to the wife - let her know it's gonna be 11:00 PM before she needs to worry. Dave thinks it's gonna run, so back down the fire roads we head back to the truck. About 45 minutes of running in 45-50 degree weather over about 15 miles with no antifreeze whatsoever. So if you pop your radiator, and if you need to make it back home, have faith it'll make it. I'm impressed to say the least.