RE: Spring choices
I just did a test for myself on my KDX. I had both sets of front fork springs. XR400 .40kg springs vs. FRP .40kg. Both sets of springs were set with 10mm of preload. (FRP 35mm spacer and XR4 9mm spacer aprox....oil levels at 100mm).
I thought that the XR400 springs would be a plusher ride because of the longer length of spring but the FRP springs seem to have more adjustability, more progessive and plusher feel on stutter bumps.
Of course this was entirely subjective. I also rode in two different spots. Either choice of these springs are a far better choice than stock. Hope this helps :aj: