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'06 Suspension Setup for Harescrambles

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Getting ready to start racing harescrambles here in the midwest. Was wondering what others have done to set up their suspension to better handle woods/trails instead of motocross. I know it will need a complete revalve, but does anyone have any pointers on a quick compromise (i.e. take 1 large shim out of midvalve, shuffle stack, etc.) to make it a little more plush? I read through Dogger's post and came across some great info there. No time to order shims before the race. Getting back into the dirt after 15+ years and I have alot to catch up on. Bike has completely stock suspension on it now, but I have the correct springs (according to RT website) in hand. Average rider. 225 with gear. Will be riding mostly woods with the occasional trip to a small track.

BTW bought this bike in a box for next to nothing. Got it back together with help from all who have contributed to this forum. Many thanks. :thumbsup:

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...i.e. take 1 large shim out of midvalve...

I don't ride harescrambles, only MX, but if I would have this "problem" , that's where I would start. slightly softer stack and more float.

I also would remove 4 of the face shims on the BV.

maybe there are some guys here that have a proven valving for you...

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I left the mid valve alone because I found it blew through the travel too much. I moved the first crossover one shim closer to the piston so it open at low speed earlier and I took one of the smaller high speed shims and made a second crossover further in the stack. Sorry I don't know which sizes exactly. I found the fork had too much high speed damping and bottoming control so the 3 stage setup softened it up further into the travel. I run 340ml of oil in the outer tubes (each side). I weight about 170lbs. and my comp is 14 out. It could still be a bit softer but it is much better.:thumbsup:

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I left the mid valve alone because I found it blew through the travel too much. I moved the first crossover one shim closer to the piston so it open at low speed earlier and I took one of the smaller high speed shims and made a second crossover further in the stack. Sorry I don't know which sizes exactly. I found the fork had too much high speed damping and bottoming control so the 3 stage setup softened it up further into the travel. I run 340ml of oil in the outer tubes (each side). I weight about 170lbs. and my comp is 14 out. It could still be a bit softer but it is much better.:thumbsup:

by adding a second crossover you get a stiffer highspeed - compared to the lowspeed.

the reason you get a plusher fork is you did soften the entire stack.

so compared to the stock stack you have a little less HS and much less LS and mid speed.

basic function of a crossover:

at low speed (rod speed, not speed of the bike) the shims only lift a little. without a crossover the entire stack has to lift.

by adding a crossover the face shims lift without touching the HS shims, so they move easier, resulting in less LS damping.

at HS the face shims hit the HS shims, so the damping gets stiffer and almost as stiff as without the crossover (only almost

the same stiffness because of the gap of the crossover shim)

it works, so be happy with it. i just wanted to enlighten the behavior of stacks...

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This is all great info. Thanks guys! Only one problem. You're talking over my head. I'd love to know which shims got shuffled and where. Thanks again.

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This is all great info. Thanks guys! Only one problem. You're talking over my head. I'd love to know which shims got shuffled and where. Thanks again.

well, ask 10 guys and you will get 10 different stacks...

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by adding a second crossover you get a stiffer highspeed - compared to the lowspeed.

the reason you get a plusher fork is you did soften the entire stack.

so compared to the stock stack you have a little less HS and much less LS and mid speed.

basic function of a crossover:

at low speed (rod speed, not speed of the bike) the shims only lift a little. without a crossover the entire stack has to lift.

by adding a crossover the face shims lift without touching the HS shims, so they move easier, resulting in less LS damping.

at HS the face shims hit the HS shims, so the damping gets stiffer and almost as stiff as without the crossover (only almost

the same stiffness because of the gap of the crossover shim)

it works, so be happy with it. i just wanted to enlighten the behavior of stacks...

So, the only way to reduce high speed damping is to remove shims? I thought by breaking up the progression, I would make it more linear. Maybe I'll play some more (I am still getting a bit of deflection off of roots). I just don't want it blowing through the travel. Thanks for the info. And if I pull it apart I'll post number for kashola that started the thread!

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So, the only way to reduce high speed damping is to remove shims? I thought by breaking up the progression, I would make it more linear. Maybe I'll play some more (I am still getting a bit of deflection off of roots). I just don't want it blowing through the travel. Thanks for the info. And if I pull it apart I'll post number for kashola that started the thread!

most stock stacks are almost linear. you can make them more progressive (which means more HS), but with just shuffle shims you can't make them degressive.

when it comes to crossover shims, its important where they are located.

near at the face shim they act like you would have opened the clicker more.

the thicker the crossover, the more you move the transition to mid speed, which lets your fork blowing through the stroke easier.

so for woods riding I would recommend a 0.1mm crossover shim after two or three face shims.

to get softer damping its best to remove some face shims.

you could add some float at the MV by removing one face shim, but that could be too much. then just remove the face shim from the first position near the piston and insert it after the clamp

some basics here:

http://www.supercross-online.de/Z/valving%20basics.htm

Edited by kawamaha

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While were on the subject, I to race hare scrambles in the SORCS series down in the SE. I have an 07 kxf250 as well and I'm wanting to get the suspension done this week while my bikes already in the shop. I weigh 185#+25# or so with gear. My stock suspension is way to stiff feeling, and def beats me up on roots and chop. I've got my clickers almost all the way soft and my rebound around 14 I think, which has helped alot, but after riding my buddies yz250 w/ the plushest suspension ever, I see mine still has a long way to go. Can I just get a revalve, diff oil weight and height and that will get me the plush woods set up I'm looking for? I want it to use the whole stroke and just float over all the roots, rocks and chop! Do I have to get springs? These things feel plenty stiff for me. I never jump big jumps, I hardly jump at all running in the woods 100% of the time. Is a revalve the right direction to go to get a "plush", Cadillac type feel....?

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... Is a revalve the right direction to go to get a "plush", Cadillac type feel....?

I cant tell you which springs you need, no experience in woods. but a revalve is the only way to get a plush suspension

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This is all great info. Thanks guys! Only one problem. You're talking over my head. I'd love to know which shims got shuffled and where. Thanks again.

still interested?

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still interested?

ABSOLUTELY! What/where is the best place for info on revalving so I can understand a little better. Very grateful for everyone's input.

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ABSOLUTELY! What/where is the best place for info on revalving so I can understand a little better. Very grateful for everyone's input.

Suspension Revalving

How Damping Works

Suspension fluid (oil) flows through the ports of the piston and up against the shims. The shims pose a resistance to the oil flow, which provides a damping effect. The damping effect is directly related to the diameter and the thickness of the shim. The shims act as a series of tiny springs, flexing to increase the flow area for the oil. The greater the flow area, the greater the oil flow and less the damping effect. The first shims that the oil encounters are the ones that affect the low-speed damping. These shims are large in diameter and thin in thickness. The oil deflects these shims easily because of their large surface area and the relatively thin steel poses low spring tension. The shim stack or valving is arranged in a taper shape. The large-diameter low-speed shims are positioned closest to the piston and the small-diameter high-speed shims are positioned farthest away from the piston. The low, mid, and high-speed circuit shims are separated by transition shims. Think of the valve stack as gears in a transmission, and the transition shims as shift forks. The more tapered the valve stacks, and the thinner the transition shim, the suspension becomes plusher in it's handling. Less plush suspension is typically too stiff to absorb the small bumps on acceleration, and too soft for square-edged bumps at speed. Much of the problem has to do with a mismatch between the piston's port arrangement and the overall valve stack.

Why Revalve?

The term revalving is often tossed around in the dirt bike magazines, but have you ever wondered what suspension tuners do to revalve a set of forks or a shock? The answer ranges from not much to a whole lot. Some unscrupulous tuners just power wash the outside of the components, turn the clickers, and charge you a lot of money. Other tuners replace the pistons and valve stacks, carefully crafting the arrangement of the valve shims to suit your riding demands and compensate for the idiosyncrasies of your model bike. Tuners need information about you and the way you ride in order to revalve your suspension. If they don't give you a survey form to complete or interview you, then be suspicious about the work they are asking to be paid to perform! Revalving can be defined as the removal, reposition, or replacement of shims in the valve stacks of the compression and rebound pistons of a cartridge fork or rear shock. Revalving should be performed when you've exhausted the basics like setting the sag, making sure your bike has the right springs, and the forks and shock have fresh oil, seals, and bushings. Only then can you make a determination whether your bike needs revalving in order to make it handle better. The main reasons why you need good handling suspension on a dirt bike is:

1) To keep the wheels in contact with the ground to provide traction and drive for the rear wheel and steering for the front wheel.

2) To minimize the impacts and vibration on the motorcycle.

3) To minimize the stress loads on the rider and prevent fatigue and injuries.

The rear wheel must stay in contact with the ground in order to provide driving force. The front wheel needs to stay in contact with the ground in order to provide steering control. Impacts on the motorcycle can cause all sorts of problems like loose bolts, foaming of the fuel in the carb's float bowl, long-term damage to the bearings that support the suspension components, and long term damage to the electrical components. The chronic problems to a rider from a poor handling bike are much more obvious. Forearm pump-up is probably the most common. Long term damage to a rider's neck and spine may take years to manifest but some people might be immediately sensitive pain. Having a professional suspension tuner re-valve your suspension might seem expensive (Average cost of total rework with parts $600) but what price do you put on pain?

The main things that a suspension system is affected by are:

1) Changes in the sprung mass from moving up and down.

2) Changes in motion like acceleration, braking, and turning.

The sprung mass of a moving dirt bike can be hard to define because the entire motorcycle leaves the ground! Technically the sprung mass includes everything except the wheels, swing arm, lower fork tubes, and the rear shock. Those parts are considered unsprung mass. Because dirt bikes are capable of jumping, gravity and the weight of the rider affect the sprung mass. The movement of a motorcycle's suspension going up is termed rebound and the movement down is compression.

Changes in the motion of a motorcycle can cause it to roll, pitch, yaw or any combination thereof. When a motorcycle accelerates the bike pitches backward. The driving chain forces try to wrap the swing arm underneath the bike. Of course that cannot occur because the shock is a finite length and connects the swing arm to the frame, but it causes a transfer of force. The rear wheel pushes down into the ground, transferring force up the swing arm and causing the front end to lift. The natural tendency of the rear wheel is to hop because the damping isn't enough to compensate for the spring force. When a motorcycle is braked for a turn the bike pitches forward, shifting the weight to the front. The rear end tends to kick because of the torque reaction of the brake caliper on the swing arm and the weight shift. When a motorcycle is turned it rolls, pitches, and yaws at the apex of the turn. A complicated motion! The front end is forced to either compress or change the fork angle or extend and plow out of the turn. Meanwhile the rear end tries to make a radial motion without loosing traction and spinning out.

Internal and External Adjustments

Suspension dampers can be adjusted two ways, internally and externally. External adjustments are limited to the riding circumstances and the adjustment range on the compression and rebound clickers. Internal adjustments are virtually unlimited because it encompasses revalving and re-porting of the damper piston and valve shim stack. The external adjusters, low speed compression and rebound, can only affect minor changes in handling. Typical low speed compression or rebound riding situations might include far-spaced shallow whoops, tabletop jumps, braking and accelerating around tight turns. All compression and rebound clicker adjusters are marked S and H, meaning soft and hard. That can also be interpreted as soft fast and hard stiff. The focus of a professional suspension tuner's work revolves around internal adjustments. When a suspension component is revalved it is also rebuilt, meaning that the bushings and seals are checked for replacement and the oil is changed. Revalving is the discipline or repositioning, removing, or replacing valve shims in such an order as to affect a change in the damper's performance.

How Incremental Valving Works

The rear shock valve stack is comprised on a series of steel washers with a variety of outer diameters and thickness, mounted on two sides of a piston. This is called a bi-directional valve. One side handles the compression damping and the other handles the rebound damping. The valve shim stacks have different arrangement patterns because the compression stack aids the spring and the rebound stack controls the stored energy release of the spring. With regards to the sizes of the shims, the larger the diameter and the thinner the thickness, the more easily the shim will bend and increase oil flow through the piston. The faster the oil flow the less the damping. Stock Japanese dampers use high flow pistons with a complicated series of shims that aren't very sensitive at slow shaft speeds. The shims don't open at slow shaft speeds and mostly the clickers control the damping. However that can cause some potential handling problems when accelerating out of turns. The bike is riding at a point on the rear spring where the clickers don't provide enough damping and the piston valving isn't in the response range, so the bike chatters. The Pro-Action incremental valving concept separates the three main damping phases of low, mid, and high. They do this by using a special piston and a valve stack with transition shims to separate the three circuits. The incremental valve stack is more sensitive at low shaft speeds so the clickers don't have to carry the damping load. The mid speed valve helps make the transition from low to high speed damping modes to give a plush ride especially under an acceleration load. The piston has smaller ports, which provide a hydraulic lock affect at high shaft speeds. That reduces the load on the nitrogen charged gas bladder and the elastomer foam bumper.

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ABSOLUTELY! What/where is the best place for info on revalving so I can understand a little better. Very grateful for everyone's input.

there is no "remove this shim and you get rid of the high speed hits"

so that nobody posted a stack its up to you if you want to try it. I can recommend you what I would do and if you try you see in which direction you go. maybe then it needs another 2 or 3 revalves, depending on your taste.

so why not try what I wrote at the beginning of the post...

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Stock Base Valve

30.1x12

22.15

30.1

29.1

28.1

27.1

26.1

25.1

24.1

23.1

22.1

21.1

20.1

19.3

These are the changes I'm thinking of making.

30.1x10

22.15

30.1

29.1

27.1

25.1

23.1

21.1

19.3

20.1

22.1

24.1

26.1

28.1

Along with taking 1 20.1 shim out of the midvalve.

Any thoughts?

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Stock Base Valve

30.1x12

22.15

30.1

29.1

28.1

27.1

26.1

25.1

24.1

23.1

22.1

21.1

20.1

19.3

These are the changes I'm thinking of making.

30.1x10

22.15

30.1

29.1

27.1

25.1

23.1

21.1

19.3

20.1

22.1

24.1

26.1

28.1

Along with taking 1 20.1 shim out of the midvalve.

Any thoughts?

the tapered part of the stack is to take out some progression of the stack. it doesn't make sense to remove shims there instead of some more face shims.

but this is not as extreme as it might sound. nevertheless, I would leave the HS shims and remove 6 30.1 face shims (6 remain) as a starting point

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there is no "remove this shim and you get rid of the high speed hits"

so that nobody posted a stack its up to you if you want to try it. I can recommend you what I would do and if you try you see in which direction you go. maybe then it needs another 2 or 3 revalves, depending on your taste.

so why not try what I wrote at the beginning of the post...

I took some of your advise on my old 07 for a woods bike a couple of years back. I was very satisfied with the result.

Just thought I'd point this out.

Cheers

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Wow...perfect timing for this post to come up. I just got a 2nd hand '06 kx250f with bone stock suspension, and I'm tearing into the forks this week to get them set up for hare scrambles. I'm a 140 lb rider (with no gear) at the fast end of the B class. All the courses down here in south florida are basically sugar sand, but there are still a lot of tree and palmetto roots mixed in. Because of that, I'm thinking I'd like to keep most of the slow speed damping to stay on top of the sandy stuff, but take out a lot of high speed damping to get rid of harsh kicks off all the roots, especially in the forks. I'm also going down two steps in spring stiffness front and rear.

Kawamaha, you mentioned there's no way to make the suspension more digressive by shuffling the existing shims...but wouldn't moving the crossover shim to the top of the stack help with that? Or, is there a better way to do it? I'm open to ordering new shims or whatever you'd think it would take.

The advice posted above about removing 6 face shims is tremendously helpful in giving me a feel for how far to go with it...didn't realize these stacks are that insensitive to changes. Thanks a ton in advance for any other advice you can give.

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Kawamaha, you mentioned there's no way to make the suspension more digressive by shuffling the existing shims...but wouldn't moving the crossover shim to the top of the stack help with that? Or, is there a better way to do it? I'm open to ordering new shims or whatever you'd think it would take.

the crossover gives a lighter low speed damping so it could be a good idea to remove the crossover shims in sandy conditions.

I don't know exactly what you need for hare scrambles. for MX and dessert you must have a relatively stiff damping, for woods you don't need that, so you can soften the stacks a good amount.

and believe it or not, you can't achive a softer highspeed damping and keep the low and mid speed the same with just shuffling some shims.

I use a HS blowoff system, smart performance offers such a system if you want to buy such stuff

The advice posted above about removing 6 face shims is tremendously helpful in giving me a feel for how far to go with it...didn't realize these stacks are that insensitive to changes. Thanks a ton in advance for any other advice you can give.

it's just a starting point. you will see in which direction you go and if you have to remove some more shims or put back some shims.

if it's still too stiff with 6 face shims removed, I would also remove one face shim on the mid valve, but in your case (sand) I would leave

the float so you have to insert the removed face shim after the clamp shim

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