99kx250 for woods

Hondaxrguy · Jan 21, 2004

I'm trying to soften up the forks for rocky rooty trails. They have had some work done to soften them up, but not enough. It feels to me like the HSC needs to be reduced more than the low speed. The front end doesn't seem to dive in corners. In fact, without getting air, it doen't feel like the forks move much at all. I'm pretty happy with the handling where sharp impacts aren't present. The constant deflecting is downright scary at times. Here's the current stack in the forks:

.1X24mm (7)
.1X22
.1X20
.1X18
.1X16
.1X14
.25X11
clickers fully out

The stock stack includes one more 24 and another 22. At the same time as the 2 shims were removed, Mobile1 ATF was used in place of 5wt fork oil. How much does this heavier oil counteract the lighter valving? Should I just go back to 5wt oil? I like using the ATF for the fact that's it's so much cheaper and readily available. Should I pull another face shim, and/or different shim? Do I need to buy a few shims to experiment with? With the current valving I consistantly have 4+ inches of unused travel. I've tried the oil level at 90mm, 100mm, 110mm, and 130mm. None seem to have too much effect on travel. I'm ~195lbs with gear, and have the correct springs for my weight front and rear.

Thanks,
Jeremy

marcusgunby · Jan 21, 2004

Now others may disagree with me here but im not a believer in the thicker oils like ATF in this type of fork,if its like a 2000KX with a stiff mid valve and no lift then it will be harsh, thicker oils make this worse.I would use a 2.5wt over ATF every time in this type of fork.IMO thats why you are not using all the travel , too stiff a mid valve.
Let us know the mid valve stack and lift, with a small lift and softer mid the base valve IMO will work.

Hondaxrguy · Jan 21, 2004

It was my understanding that the midvalve did not come on the bike until 2000 mine is a 99. If I'm incorrect, how do I access the midvalve?

Jeremy

marcusgunby · Jan 21, 2004

95 the mid came in, 1999 has one but i think its like a older 96 YZ fork.Any bladders? i think they came in in 2000.Need to see a pic of the catridge to help on getting to the midvalve, but the late model kx forks generally have a removable bottoming cone, it has 2 flat on it, you need to grind down a open end spanner to undo it.Once youundo the cone it has a slit wire ring inside so be carefull when you open it up, it will come clear when you remove it, just do it slow and watch where each part comes from.

Hondaxrguy · Jan 21, 2004

Don't see any bladders. Assuming that rebound is on the side of the piston closest to the nut that needs to be ground down, here's my midvalve stack (stock):

.1X20
.1X25 (4)
.1X23
.1X20
.1X17
.3X12
.1X15
.1X17
.1X20
.1X22
.3X25
.1X20

Not sure how to measure lift.

Jeremy

marcusgunby · Jan 21, 2004

Lift is the amount of movemnt the stack has, ie it can move freely for say 1mm than it hits a stop, this free movement is normally controlled using a small spring, im guessing on yours it has a o ring behind the stack and no free movement at all?? if this is the case you need to buy a spring from somewhere like Racetech and adjust the midvalve for some free lift(float its also called) do a search on midvalve and you wll get lots of uselfull info.

i would reduce(soften) the low speed side of the midvalve and set the lift to 1mm.

bclapham · Jan 21, 2004

it depends, one way is to build the mid back up and then stick a feelr guage inbetween the first shim and the face of the piston. you might be able to get away with putting the 20.1 and 17.1 behind the 12.3 clamp shim.

Hondaxrguy · Jan 21, 2004

Marcus- I have the o-ring and no spring. I may order the spring, but would like to put the bike back together for this weekend.

bclapham- so moving the shims the way you're talking about, I'd end up with a stack like this?

20.1
25.1 (4)
23.1
12.3
15.1
17.1 (2)
20.1 (2)
22.1
25.3
20.1

Is that correct? What is the purpose of the "hourglass" stack? And the smaller 20.1 at each end? Are the 20.1's there to allow a small amount of flow without restriction from the shims?

If I do make these changes, and go to 5wt or 2.5wt oil should I leave the base as it is, or soften that more as well? I have no idea how big of an effect these changes will make.

Thanks,
Jeremy

Jeremy

bclapham · Jan 21, 2004

yes- although i am no tuner, to the best of my knowledge, taking out those shims should lessen the HSC. i think the reason for the hourglass shiims is to 1. give the mid shims room to bend and 2. setup the appropriate lift.

there has been a lot of talk on this forum before about low lift midvalves and the use of ATF oil- ive had little sucess with either when looking for a plush fork (i ride really rough, fast outdoor mx tracks that arent that jumpy), but like i said, i am not a suspension tuner nor am i a really fast rider- but i can tell the difference between a fork that works well and one that ruins my day because it is so harsh.

Hondaxrguy · Jan 21, 2004

After reading up more on the midvalve on the kx more specifically, the smaller 20.1 seems to be there to provide .1mm of lift. So would moving 1 or both of the shims in front of the first 25.1 have any effect other than increasing lift?

Jeremy

marcusgunby · Jan 22, 2004

There was talk of that shim providing a small bleed effect and if you remove it , it affects the rebound, i havnt noticed this.Once you remove the o ring you may find you have more lift that you want, and will have to add a washer (at the bottom of the stack)to space the stack.

Hondaxrguy · Jan 22, 2004

Marcus, hopefully I'm understanding this correctly. Lift would generally have an effect on LSC while the midvalve stack has more effect on the HSC. I'm fairly confident that with the 5wt oil the LSC will be soft enough. So, if I remove the shims talked about above, putting them behind the clamping shim shouldn't have any negative effect? I still don't understand why they use shims behind the clamping shim to provide the correct lift. Why not just a spacer? Do I really need to remove the o-ring and increase the lift? If so, how much lift should I have? Now that I know that my setup has no lift, I understand how to measure the lift.

Thanks,
Jeremy

joereitman · Jan 22, 2004

Happy with the mid to check valve mod to my 03 kx250 forks. Don't know if this helps regarding your 99...

marcusgunby · Jan 23, 2004

The later forks do just use a spacer-they do all sorts of weird things over the years,as to removing the or ing, even for harcore mx i couldnt get a fork plush with the std no lift midvalve.1mm is not alot of lift, but it will work well IMO with your base valve.

Hondaxrguy · Jan 26, 2004

Well, I put everything back together today, but didn't get out for a ride. I ended up leaving the o-ring in because I don't have the spring yet, but plan to order the spring for future testing. I moved the 17.1 and 20.1 shims like talked about before. I'll post up what I think about the forks once I get to ride. Thanks for your help guys!

Jeremy

Hondaxrguy · Feb 2, 2004

I got a little seat time on the bike today and the forks are much better. I seem to be using almost all the travel now. The forks soaked up a lot more of the trail junk, but never felt like the forks were diving or wallowing. I set both clickers to 10 out, and didn't even feel the need to touch them. Next weekend I'll go out and do some testing with the clickers to see how they feel. I'm not sure if I'll need to go back into the forks for more work or not. I was happy with them today for sure.

Jeremy

99kx250 for woods

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