Well here goes, susp changes what do you think?


Feb 1, 2001
99KX 250
Current settings: Forks comp full soft, rebound in the middle, spring: stock (I think) pink dot marked on spring. Oil level 90mm from top w/ springs out, Mobil 1 atf.
Action is (very) harsh during first few inches, I can feel all small bumps. Next part of stroke seems to be good, worked well through some unexpected deep whoops encountered at a faster than expected speed, tracked well, but did not bottom.
Rear Shock is set up a little soft (settings only & will stiffen a little later on, otherwise shock is very good).
Is this fork action inherent on USD fork?s. I cannot afford to revalve or respring at this time.
I am thinking of going to a 2w or 5w oil (Mobil 1 is 7w Right?) and lowering oil level to 100mm to start from.
Should I go lower with oil setting? I would like to try the 2w first.
Silkolene synthetic is available, but I might be able to find KYB O1 ( I believe thats what it is).
I am 195 pound rider, off road only, no radical jumping, however I would like the suspension to work ok if a the occasional jump occours. Fork seals and oil serviced recently.
Just looking for your thoughts on levels, wts, and brands of oil.
My feelings are that if comp is full soft and harshness is there. by trying what I propose I can get the usefullness of my clickers farther into the middle. I realize that there is no substitute for revalving and profession tuning, but until I do this, I can try different settings, and at least improve on what I have now.
Well what do you think? :think :think :think


Aug 25, 2000
Disclaimer: I do not purport to be any sort of expert..on suspension or otherwise....

Ok, that being said...as I understand it M1 atf is about 7.5wt. As far as lowering oil height, this will only effect approx. the last 1/4 of travel, not quite what you are looking for, I think.

First suspect would be the springs...I'm not sure, but I would suggest first you determine if the spring weight is right for you. I think KXs still use progressive rate springs as well, which may also be causing some issues. Although, I personally, have never had to deal with them, I am sure that the suggestion of straight rate springs will come up.

As far as tuning with oil weights...I'll leave that to the fluid dynamics experts to explain in detail, but I would suggest it should have an overall effect, although you will likely loose some "clicker effectiveness".


Aug 31, 2000
hi, if you mean that the fork action is very harsh for the first few inches.

did you change your fork seal before? if you do, maybe you can check out your inner and outer bushing. The teflon coating maybe worn off and causes the initial harsh feeling from the beginning of the stroke.

i got the similiar problem with this after i revalved and changed the seal for my friend 98 YZ125. i thought is the compression valve, but found out is the worn bushing that is causing the problem.

hope this help:D


Feb 1, 2001
The teflon coating is intact, and the harshness seems to be about the same before and after I changed the seals, I will be checking sag this week. In the mean time it looks as if I'll be looking forward to lessons on fluid dynamics. Thanks to all who have, and will be replying. I appreciate busy people taking the time to post to my dilema,,, or possibly they too lack the creativity that I seem to, and spend all their time either riding on, thinking about, working on or surfing about DIRT bikes!!!:eek: :eek: :eek:


Apr 10, 2001
This may not help you at all, but I think i remember reading in one of these forums a while ago that the 99 onward KX's have progressive rate springs, and the 95 - 98 KX's have straight rate. I think people were changing the progressive for the straight, and getting good results?? I wouldn't know, i am happy with my bike as it is, but I am far from pushing the suspension to its limits :silly:
Oh well, i hope this can help you in some way or another!!



May 3, 2001
Well at 195 lbs. you are a bit heavy for the stock springs. Soft springs combined with the stk. midvalve set-up will let the forks ride down in the harsh part of the stroke. By stiffening up the forks (stiffer spring) the bike will ride up in the stroke better which gives you more usable travel thus feels plusher. Since this will transfer more weight to the back now you may find that you will need to stiffen the rear also.



Jan 9, 2000
I have reread your post and ive missed a few key factors.Like others have said the std springs may be too soft causing harshness and i adgree with others the progressives fitted to 99 were very poor and should be replaced with the correct straight rate.The 2000/2001 has a straight rate so it the right way to go.Always remember the springs are the building blocks of the suspension which when wrong will not allow the suspension to ever work as it should.

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