Xr400 forks drop right in, plug and play. I did this mod and am very happy with it, huge improvment. I found forks, clamps and wheel for $200 on Craigslist. You can reuse XR250 brakes and wheel, but you'll have to change the wheel bearings to accept the XR400 axle and the spacers,speedo drive,seals too. I think this is the easiest, cheapest upgrade one can do to the XR250 suspension. However, to get the most out of this upgrade you will need to spring them for your weight and do the shim stack mod (remove 6 shims from the compression stack).
Edited by Enc_1, 16 April 2012 - 08:56 AM.