I have owned a 98 YZ400 (that ate 3'rd gear),a 2004 WR400 (good bike), a 2007 YZ450 (broke a crank), a 2008 YZ450, and now a 2010 YZ450 that just ate a 5'th gear. I bought another motor that also had a broken 5'th gear. Now a friend has a 2011 YZ450 that has been completely rebuilt because it broke a 5'th gear. Seems to be a pattern! I love the bike, but tearing down transmissions is no fun. I would like to buy another YZF, but have serious doubts about the reliability. Anyone else having 5'th gear problems?