Sounds like you ran it to long and it's welded in the bearing. We have a friend that maintains his KLR when it breaks. I changed my rear bearings at 22,000 miles, did they need it? There was a little slop in the carrier bearing, I might have gotten another 5,000 miles out of it, for $17 dollars I changed all three of them for piece of mind. I took the old bearings to the local bearing shop and bought bearings that were twice the quality over stock, seals on both sides. This friend has run his bearings to failure. Personally I would have noticed something was wrong before the sprocket carrier cut part way thru the swingarm. He's the rider that changes one sprocket or just the chain. We all know they should be changed as a set. The crazy part is, he has the money, he's just cheap. He will squeeze a quarter until the eagle screams. I change parts/tires when I have used 70% of their life. The next crazy part is, he wants my used parts. We rate our rides on how many parts fall off of his bike or how many times our other friend falls over on his KLR.