KX Forks, revalve?

Questions and comments about converting to beefier forks..
robkdx
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KX Forks, revalve?

Post by robkdx »

Starting to get some time on my KX 2000 forks on the KDX. When building it up I removed 2 of the big shims from the stack and added float to the mid.

But its punchy over high speed hits and Im only using 110mm of travel.

Remove a couple more big shims from the foot valve? Can I pull them out with out removing the forks from the bike?
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KX Forks, revalve?

Post by robkdx »

Just had a quick look at it and its very stiff to move, thinking its needing a chunk of grease under the seals. Wonder if thats the issue.
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Re: KX Forks, revalve?

Post by bradf »

Was there a bladder in the KX forks?
What spring rate? and your weight?
New bushings that are not binding?
Oil level and weight?
Base valve is very easy to remove.
How many 24mm shims were there originally and how many are there now?
What is the entire shim stack? The shims behind the 24's limit the 24's ability to flex.
'04 220 w/'01 KX250 USD forks, '02 RM125 Showa shock, Rekluse EXP 3.0, LHRB & all RB'd
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Re: KX Forks, revalve?

Post by robkdx »

bradf wrote:Was there a bladder in the KX forks?
What spring rate? and your weight?
New bushings that are not binding?
Oil level and weight?
Base valve is very easy to remove.
How many 24mm shims were there originally and how many are there now?
What is the entire shim stack? The shims behind the 24's limit the 24's ability to flex.
Bladders are gone. Stock spring, im 105kg. 5w oil. cant remember level. removed 2 24s from stock stack.
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Re: KX Forks, revalve?

Post by bradf »

If there were 11 each 24's in the stock config, then typically 7 were removed. That leaves:

24 (4)
22
20
18
18
14
11
Thick spacer

High oil level will be significantly harsher. 120mm is preferred.
'04 220 w/'01 KX250 USD forks, '02 RM125 Showa shock, Rekluse EXP 3.0, LHRB & all RB'd
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Re: KX Forks, revalve?

Post by robkdx »

Righto. I only took 2 out. and my level is 100mm based on this. http://www.thumpertalk.com/topic/572915 ... pic-heavy/

Time to find that 14mm allen key.
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KX Forks, revalve?

Post by robkdx »

Found the allen key. Also greased the fork seals with fork grease. Its moving a lot better now. Ive not ridden it in 16 months so they must have dried up. They will get better with the next ride as the grease gets about.

But will drop the base valve and drop some shims and lower the fluid level.
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Re: KX Forks, revalve?

Post by bradf »

Here is some old info I dug up for my 01 KX 250 forks

Fork Shim Valving for 2001 KX250

.43 kg Spring for 185-195 lb rider load

Bladder assembly removed. Restrictive barrier modified. (must do this to eliminate mid stroke spike)

All shims are .1 mm

Base Valve torque to 40 ft/lb use blue Loctite OIL LEVEL 120 mm
Use Golden Spectro 85/150 (true 5 wt)
Nut torque to 48 in/lbs
Cup edges facing ↓ Oil is forced ↓ this direction on compression
Spring
Washer/Sleeve Check valve portion
Piston valve assy
24 (4) Removed 7, was (11 stock)
22 22 can be removed for plush ride, not recommended for advanced riders or jumps
20 Low Speed Compression Circuit
18
18
14
11
Thick spacer
_____________________________________________________

Cartridge Assembly

Nut torque to 48 in/lbs use blue Loctite
Thick washer
11
14 High Speed Rebound Circuit
17
20 . . . . . . . . . Oil is forced ↑ on rebound
13
23 (3) face shims
Piston
20 bleeder shim removed this (or susp. will shoot through first few inches of travel) leave in for trails use an 18 to soften further for slower riding
25 (3) High Speed Compression Circuit (2) for very plush ride, but will increase possible bottoming
22 this shim can be removed for very rocky trails
20 Oil is forced ↓ on compression
17
15
12 this is a transition shim separating the 2 stacks but it affects both
…………………………………………………………………………..
15
15
17
20 Low Speed Rebound Circuit
22 Oil is forced ↑ on rebound
23 (3)
20 this is a bleeder that allows some unrestricted oil flow past
O-ring
Cup edge facing ↑
rod


Bladder must be totally removed to include rubber bladder, springs, and white plastic collar hardware.

Restrictive barrier (RB) is the machined thin washer that sits directly below the main spring. Its purpose was to actually restrict oil from blowing up through the 4 holes it covers. Once the pressure of the spring was overcome by the compression and oil pressure it would flow around the RB.

RB modification:
Drilling holes is hard to do AND if the holes are in the center of the RB the spring will still cover them.
Use the corner of a bench grinder wheel to grind 5 deep slots into the outer edge of the RB. Alternate method is to machine slots. The slots should go past half way into the RB so that at any position one of the 4 holes will be un-covered below it. The reason to keep the RB washer is to keep the spring from gouging the plastic it rests on. The RB will now allow unrestricted oil flow up through an uncovered hole.

A mid-valve check-plate assembly similar to the BV check plate (cap, spring and washer) can be removed. Add the shims directly behind the MV piston (HSC and LSR) to create a true MV HSC stack. Check-plates must be set to a specific “lift” or free play and they are NOT progressive but rather digressive in nature. Check plates were an easy solution, not the best solution.

Do not remove the 22’s (Grandma shims) unless a lightweight kid or girl is riding this in which case the springs would be significantly less, like .38’s. It will be plush for slow sharp edge bumps but any aggressive hits at speed will tend to make the nose dive, which brings its share of handling problems.
'04 220 w/'01 KX250 USD forks, '02 RM125 Showa shock, Rekluse EXP 3.0, LHRB & all RB'd
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KX Forks, revalve?

Post by robkdx »

Wow thanks Brad. I can work with that.
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KX Forks, revalve?

Post by robkdx »

I think I have found part of my problem. The fork was sitting at rest a long way into its stroke. Removing the carts found around 60mm that the fork would not extend at rest.

So my BV stack is
24 Yes only one.
22
20
18
16
14
12
11
2 x thick washers

Rebound
11
14
17
20
13
23x3
piston
20
25 x3
22
20
17
12
15
17
20 x2
22
25
spring

So i think I will add 3 x 24 to the comp as when I took 2 out it only left 1. Remove the 20 from the MV. I have the perfect washers to remove the RB. May remove 1 25 from the high comp as I dont jump and ride slowish bush trails with heaps of roots.

Think I need to add some preload to the springs, maybe 15mm static.

Thoughts?
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Re: KX Forks, revalve?

Post by bradf »

The single 24 in the base valve would really allow a lot of oil to start transitioning very quickly = nose diving easy on any hit-hard front braking-cornering in a rut. Don't add any preload. The correct spring rate and length for rider+gear weight is more critical. Just as oil level is critical. 120mm is the center. Adding 130mm will effect feel as will 110mm.

The last shim in the rebound is a 25. You could take one of the 20's between the 17 and 22 and put it last next to the o-ring. This is the low speed rebound circuit so it is easily adjusted and not critical if you do or do not change it. Most of us putt-putt trail riders will never ride better than these forks can deliver any how.
'04 220 w/'01 KX250 USD forks, '02 RM125 Showa shock, Rekluse EXP 3.0, LHRB & all RB'd
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Re: KX Forks, revalve?

Post by robkdx »

bradf wrote:The single 24 in the base valve would really allow a lot of oil to start transitioning very quickly = nose diving easy on any hit-hard front braking-cornering in a rut. Don't add any preload. The correct spring rate and length for rider+gear weight is more critical. Just as oil level is critical. 120mm is the center. Adding 130mm will effect feel as will 110mm.

The last shim in the rebound is a 25. You could take one of the 20's between the 17 and 22 and put it last next to the o-ring. This is the low speed rebound circuit so it is easily adjusted and not critical if you do or do not change it. Most of us putt-putt trail riders will never ride better than these forks can deliver any how.
As per the thread in thumper talk I have changed it to have 1mm float so a spring there now not an o-ring. I will leave the preload alone then.

Thanks for the help.
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KX Forks, revalve?

Post by robkdx »

Just got it back together. Different fork. Way better. Will be a week before I can go for a good ride but just sitting on it feels good.

Next will be working out the right spring rate.
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Re: KX Forks, revalve?

Post by robkdx »

Thread dredge.

I never changed the valving but only just started riding the bike again. What Im finding is when standing going down hill Im getting pounded by braking bumps. Everywhere else it feels fine.
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Re: KX Forks, revalve?

Post by KDXGarage »

What is your weight in full riding gear currently?

Did you ever change the spring rate?

A whole millimeter of float sounds like a lot to me.
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Re: KX Forks, revalve?

Post by robkdx »

110 kg geared up.

Spring is .41.
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Re: KX Forks, revalve?

Post by KDXGarage »

robkdx wrote: 04:29 pm Feb 17 2019 110 kg geared up.

Spring is .41.
You might want to look into getting a stiffer spring in there.
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Re: KX Forks, revalve?

Post by robkdx »

KDXGarage wrote: 12:50 am Feb 18 2019
robkdx wrote: 04:29 pm Feb 17 2019 110 kg geared up.

Spring is .41.
You might want to look into getting a stiffer spring in there.
Im not using anything like all the travel so the spring weight in my opinion is not the issue.
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Re: KX Forks, revalve?

Post by KDXGarage »

If the fork is working properly, then the valving is way off. It may be time to pay someone to check it out and revalve it. If you are 110 Kg going down a hill, then it should be further into the stroke.
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Re: KX Forks, revalve?

Post by robkdx »

Going to strip them tomorrow, maybe i did chage valving. May even remove float from the mid valve and get tova known point.
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