I have a 2007 YZ450f. an oil seal burst and it ran without oil for about 10-15mins. Full engine strip later and everything on the inside of engine is fine/ or been replaced but it wont stay running. I stripped the top end then and found that the inlet cam was very stiff, nearly solid. The inlet cam was leaving scratch marks in the cam cap and cylinder head that the cam runs in. oil pump works fine. all oil lines seem to be clear. I can rub down the scratches but it only runs for a minute. Only damage i could find was the ball in the end of the cam cap is damaged and out of place. Any ideas why this could be happening???