My son has a 2009 Yamaha WR450 that the block in the bottom of the swingarm broke off this weekend riding at Anzo-Borrego. Looking at it the welds(heliarc) didn't penatrate the metal, in fact the one on the back side the surface of the swingarm is still smooth. Wondered if any one else had this happen. They don't make a replacement piece as it is considered to be part of the swingarm. I have the old piece, but it is tweeked after going around and bending the sprocket. Not sure I can straighten and get proper alignment for the guide if I get it reattached.