I have three left-side case covers with the added hole like in the picture above. I think the theory is that previous owners added the hole and routed the crankcase breather to it so that engine blow-by would lubricate the chain. However, I measured, and the holes in all three of my covers are in exactly the same spot and are the same diameter, indicating that these were mass-produced this way. You also see a lot of these covers with holes in them on eBay. Is it possible that some XS650 sprocket covers left the factory with these holes? Any thoughts?