Another board has a long thread on this. While not cheap, it is an OEM upgrade. If you are going to do a rebuild that would be the time to do it. I'm strongly considering it.adam728 said:Looking for your YZ250? Many people use 3rd, 4th, and 5th from a WR426 for 02-07 YZ250's. 3rd is about the same, 4th is a little taller, and 5th is much taller (around 15% more than the stock gearing). I know a guy that did it and loved it. If I need to split the cases on my bike there will be some WR gears going in!