Jer, all; what spring rate, oil height, preload?

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#1
Jeremy, I have a 99KX125 and have been going crazy with the suspension. I am 140+- some pounds and ride a supercross style track with some HUGE jumps, SHARP rocks, and some fairly gnarly chop in and out of turns. I have installed 250 stock springs, run 8 mm preload in the forks, 95mm sag on the shock, and a 95 mm oil height, and 5wt oil. I have the comp clickers almost at full soft, and the rebound in the middle. The suspension absorbed small bumps well with the stock springs, but bottomed really hard over almost all the jumps and kicked me front end high. the 250 springs are not bottoming much at all(only when I case or overjump), but they are harsh over small bumps. They are not rough, just firm, they don't absorb crap to be blunt and it is beating me up over the rocks and the bumps. I am torquing the clamp bolts and the linkage bearings are in perfect condition.
I know that if the progressive sprngs stinkbug, they become very harsh because they run in the stiff section of the spring, but in the video that I have of me riding, they are in the top 0-3 inches of travel when I am going over the problem areas. I know you may say straight rate springs are in order, but I think for the bottoming resistence that I will need(ie, very stiff spring, like 250 spring), the initial part of the travel would be much stiffer and harsher. Please recommend spring rates, oil heights, oil weights, preload, etc., I would really appreceate it if you could also explain why these recommendations are made. Thanks.
Also, I can not afford revalving at this point, and if I got it revalved in the future, would I need to get another set of springs other than the ones that you recommend now to go with the revalving?
Thanks again

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Aaron's web site
 
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#2
Check the Race Tech set up guide at http://4.22.116.247:81/cgi-win/racetechv2.exe

This is just a reference point to start from. Forget what their valving recomendation would be (it won't show you), but it will give you the spring rates, oil height, etc for your weight and riding style.

From there you could do your own valving mods for the cost of a few shims and oil! Going with the right springs for your weight is the most important thing.

Add a little low speed compression for jump landings and g-outs and remove some high speed compression for the sharp rocks, braking bumps and stutters and you'll be 85% of the way to that fully tricked out suspension for the cost of an oil change and a 6 pack!

Revalving is pretty fun, albeit quite time consuming.

pete http://www.verts.com/dirt/
c3hammer@verts.com


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Pete Carney
c3hammer@verts.com
 
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#4
Nope :)

Supercross type tracks get your suspension moving about 8 - 9 meters/sec max. Rocks and roots get it moving 11 - 13 meters/sec max.

You can almost completely remove the high speed shims from your stack and it won't effect the bottoming resistance at all! OK, that's an exaggeration, but still somewhat true, depending on what's in your Kayaba forks. For the Kayaba shock, it is totally true.

I struggled with this concept for a long time. All the work in valving is controlling how much the low speed shims open and at what speed. All the oil has to flow past the face shim one way or another.

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Pete Carney
c3hammer@verts.com
http://www.verts.com/dirt/
 
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#5
Okay, if I do the valving mods, will I be able to ride MX too, or will my bike be supercross only? Also, where can I get a nitro tank and valve to do the shock myself so I don't have to pay the dealer every time I rebuild it? How much will it cost? If I post my valving now, will you guys help me sort it out? Last, but not least, If I get the right springs for the stock valving, will they work with the modified valving or will I have to get new ones? Do the adjusters(shock hi/lo) affect the suspension as you have said? I am really confused and this is the total opposit of what I have heard from anyone, even well established tuners.

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Aaron's web site
 

Jeremy Wilkey

Owner, MX-Tech
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#6
Kawie,
It's not quite that simple IMO, but what Pete mentioned is acurate. Botoming is not a highspeed issue..

The high and low speed adjuster orfices and preloads shim stacks inside the unit. They do a fair job of creating a variable orfice for the lower middle speed range. But it is more of higher and lower range not a high and low speed adjustment..

Regards,
Jer