I decided I'd give my chain a little clean because it was the weekend and I had a few minutes but mainly because I've never cleaned the 250's chain. Although I lube it regularly I don't take the best care of it or its chain. To compound the issue, its the same chain as when I bought the motorcycle, and I dont know how well the previous owner took care of the chain. Upon taking it off and giving it a thorough clean (caked on dirt and lube), this is what I found: Since I ride the 250 as if she were my ex's hot younger sister, I can imagine I put a lot of strain on the chain and therefore inspect it here and there to make sure there are no life threatening issues with it. Unfortunately this crack was on the inside of the chain, which is the conveniently neglected side. To make things worse, when I was taking the chain off, I noticed that my front sprocket nut had come loose too! The bent washer wasn't as bent any more and the nut was around 4 spins away from popping off. Hope this serves as a reminder to you folks about visually inspecting the IN side area of the chain as well as paying attention to the outside. While at it, pop the front sprocket cover off and make sure everything is nice and secure in there. Shouldn't take more than 15 minutes, and could save your life and/or wallet. That section of the chain is the only portion that is rusted, and both my front and rear sprockets are in A1 condition so I'm at a loss as to why this happened, any ideas would be good to take into account. Does battery acid cause rust? I hear that a standard chain is better than an o-ring, as long as you lube it regularly (o-rings apparently get dust and debris lodged in the rings causing higher friction and more damage, and on top of that require regular lubricating as well). With the lack of the markedly superior x-ring chains of 428 pitch, I was thinking of getting a standard chain, or should I stick with an O-ring?