It looks like he has an 04 or 05 model, they didn't suffer the same stink bug feeling as the 06 and 07, mostly due to not having a high speed compression adjuster.
lower the forks so the tops are flush with the clamps,check Race-Tech for the proper spring rates for your weight, get them revalved by a reputable suspension company, They guy I use is Race-Tech certified but he uses some other companies products as well, set the racesag at 93mm, to 95mm. I have found great success with the 93mm setting. you might also consider running a 20 or 22mm offset tripleclamp, I believe that the kx450 from 04-07 will cross fit w/ the 03 -07 kxRs