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Message: [QUOTE="dirt bike dave, post: 1433463, member: 18302"] I agree on insufficient lube and not enough warm up. FWIW, I've heard that when a cold motor seizes due to insufficient warm up, there is often evidence of damage on the on the intake side. A contributing factor could also be engine braking while riding on the road, without pulling the clutch in. High rpm = lots of friction, and throttle closed = not much lube or fuel to cool things down. I grenaded a CR250 after a sustained top gear run on a road, then coasting in gear...the crank bearings and big end bearing failed and a hole got punched in the cases. FWIW, the motor was plenty warm and I was mixing 32:1. I now pull in the clutch and avoid high rpms with the throttle closed. It was an expensive lesson. [/QUOTE]