I have a 99 YZ400 and whilst riding the other day I was in 5th just cruising the bike locked up. I tore down the engine yesterday to find the conrod has failed just below the small end. It has gouged out the cylinder, destroyed the piston and on splitting the cases I have found 4th gear (input and output) shattered on a couple of teeth, a shift fork rod has also come loose causing the lugs for the rod in both cases to break off. I imagine this would mean both cases are now junk. On further inspection the crank around the big end area has gone blue either side of the big end crank pin. My question is, what does anyone think has happened. What has failed first and what the hell should I do. Repair or New Engine. Just for info, I don't race the bike, It is regularly serviced and looked after extremely well. It hasn't got many miles on it also. Has anyone heard of this happening?