J-YZ replied to kennythump666's topic in KX450FI had about the same thing going on. I was servicing my forks and found that the inner fork tube would not extend all the way out. Service manual said it should extend all the way out. Put new springs 1.8 and 5mm spacer with the spring. Now It rips. I think it would be worth checking. I almost sold this bike 09kx450. Now I love it.
J-YZ replied to kennythump666's topic in KX450FOne of the problems I found in forks 09 450 was in the inner fork system. When I serviced the inner system I never could get it to fully extend on its own. Put 1.8 spring in it added 3mm preload extended properly. Made the bike handle and turn much better. Then bought Applied 22mm. Now this bike is awesome. Just my opinion.