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!
Currently I just swap between a 13, 14, and 15 tooth front sprocket depending on the terrain.
Sure I could change the sprocket, but i would still like that pull down low though. I wouldn't split the cases for just that, but if/when I need to, im going to seriously consider it. Definately depends on the money... ha. always does.
Do you have to replace 3rd, 4th, and 5th? or can you replace just 4th and 5th?
If I did the math right... 3rd for the WR is .76 and 3rd for the yz is .78.
I think the wide ratio gears swap out of some WR's, that would be the cheapest way to go. Most gears are about $60 a piece. So, to do a 4th and 5th gear swap would be about $240.
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!
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.
FYI.
I have "heard" that the DRZ400's tranny gears also interchange with the RM250. For our enduro type stuff, a granny-low would be good for pushing brush (no trail) and a tall fifth for blacktop. We'll be going thru my RM's lower-end soon........we'll see.