2005 CRF with nearly seven years of hard desert racing and riding on her. Have done two top ends since original, last one in late '09. This happened last weekend on mile 30 of a 100 mile race. She lost power, I heard a clunking sound, then shut her down. No strange noises before that. There was not a drop of coolant in the tank afterwards, but it was full before the race. Almost all of the engine oil was pushed through the valves, through the carb, and out the airbox. My theories - 1. coolant system leak and damage caused by heat. 2. Never replaced rod and crank bearings, excess freeplay in piston, caused all damage, all rad fluid boiled off but not root cause. 3. Overdue for top end, damage caused by warped piston? Any thoughts? Can anybody spare me a thousand bucks or so?