DT125R FORUM

I have recently rebuilt my dt125r engine, the engine was running fine when doing the heat cycles, I ran the engine on idle until up to running temperature and then waited until it was cool before running it again. I repeated this 5 times before riding the bike. It was running fine for approximately 2 miles and then the engine made a high pitched sound and then locked up. On inspection I found the mains bearings had failed. Any advice on what would cause this or any advice on what I have done wrong. I replaced all bearings and seals with koyo bearings that were brought from eBay. Anyone else had this problem or any advice would be greatly appreciated