97-04 KX500 / 96-97 KX125/250 swap - height & valving, vs KLX300R

Questions and comments about converting to beefier forks..
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Re: KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by Chuck78 »

On another note, I topped out my stock KDX front end to measure, and I don't even have the advertised 11.2 inches travel worth of clearance between my 90/100-21 front tire (1 size bigger than stock) and the fender!!!! Looks like I'll be internally travel limiting the KX500 forks then... now I need to get my lathe put back together!!!! Been in pieces since the move...
The KX forks being 1" taller could really create a dangerous bottoming out / front wheel lockup situation if I just dropped the triples on the forks (i.e. raised the forks in the triples) to lower the front end as most people say they do on the KX fork swap...

As far as numbers go however, I have often heard that travel numbers are skewed slightly because they are measured with the top out springs forcefully topped out out to the point of coil bind on the top out spring.
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Re: KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by KDXGarage »

Measure twice, cut once? :grin:
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Re: KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by 6 Riders »

If you are internally lowering the forks, consider only going 3/4" and consider the extra quarter a little extra adjustment room.

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KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by Chuck78 »

Reducing the preload to increase the rear shock static sag helped out dramatically on this past weekend's trail riding! Thank you for pointing out the obvious, Jason. For some reason I thought that I had plenty enough sag, Loosely going off of approximately one-third of the total travel as proper sag amount. Needed slightly more.

My street bike blew up and have many obligations with remodeling help, so I have not been able to get to the KX500 fork rebuild and revalving yet. I'm still looking for tips on exactly what my compression stacks starting points should be for woods riding.

My brother is riding a CR125 in the woods with me, 2000 model. To get rid of the motocross compression damping issue in the woods, could he just run thinner fork oil and add more rebound damping on the clickers? That would also be a good question for the KX forks, but they are off the bike already, so I definitely want to rebuild them and adjust the shim stack appropriately. My brother doesn't want to do that much work to his.
I'm assuming it runs 5w oil or so, and potentially he could run 2.5W. I just wondered if that would have a similar effect, or if the spread between rebound and compression would not work out with just a viscosity change.
I've been working on trying to get him off of that bike and onto a real trail bike, a KDX, and even offered him mine if I happen to get in 86-88 KDX 200, which is what I really wanted. I suppose the 77 PE 250 will help satisfy my fix for an air-cooled monster, but the 86 KDX 200 would be far better on the trail...
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Re: KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by KDXGarage »

Good to hear that the preload helped out.
I have never tried switching to a lighter shock oil. Is the shaft and stacks not going to have to be removed to change the oil?
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KX500 swap - re-valving?

Post by Chuck78 »

My bike is very tired and time for some serious overhauls, building up another engine with Ron Black carb, head, and a ported replated overbored cylinder.
I figured it's also time to do the KX front end swap. I have been sitting on these parts for a minute now. Life gets in the way of everything fun! Especially the older we get.

Can anyone point me in the right direction of any tutorials or videos on basic revalving of this type of KYB cartridge? I was looking for any specific info on what people have done with the kx500 shim stack to make it better for woods, or the KX 125 or 250 Forks that are similar. Late 90s. I haven't had much luck other than one thread of someone saying they use a YZ 250 cartridge instead because the valve body looked to be able to flow a lot more than the KX. I might just buy Race Tech gold valves, but if I can do this myself without the expensive racetech internals, and end up with equally good results, that is definitely a plus.

Also I still am unsure if the .40 kg Springs will be too much. I would have preferred the 96 or 97 KX 125 Forks, as they basically have a KLX 300 spring rate, which should be perfect for me.


Now that we have my brother's 2000 cr125r tuned a little better, added flywheel weight, put on tubliss and good tires, backed the compression all the way out, riding his, that bike feels completely rigid, no frame flex, no fork flex, and very much a completely different ride than the KDX of course. A lot of that is the aluminum frame, but the steering definitely felt a lot more accurate and very rapid.
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Re: KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by KDXGarage »

Which year KX500 forks do you own?

Have you taken the base valve apart and measured the shims?
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Re: KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by Chuck78 »

97-02 KX500E forks. I cannot recall the exact year off the top of my head but I am thinking it was a 2001.
I have not dismantled them yet, as bench space is at a premium at present, and wanted to have all info at hand when I found a block of time to tear them down.

I may be doing some KDX250D forks for a friend sooner now, after a bad crash this past weekend accelerated the failure of his 43mm inverted fork seals. I'll be posting up suggestions for that one to be re-valved here later on.

This seems very helpful for both as far as I can tell:


http://www.kdxrider.net/Kayaba.htm
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Re: KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by B737driver »

I had a local reputable suspension guy re-valve my KX forks. He recommended internally shortening by 3/4”. It works well and I haven’t noticeably bottomed them out....yet. FWIW. Good luck with the new ride, you’ll like it.
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Re: KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by KDXGarage »

Chuck78 wrote:97-02 KX500E forks. I cannot recall the exact year off the top of my head but I am thinking it was a 2001.
I have not dismantled them yet, as bench space is at a premium at present, and wanted to have all info at hand when I found a block of time to tear them down.

I may be doing some KDX250D forks for a friend sooner now, after a bad crash this past weekend accelerated the failure of his 43mm inverted fork seals. I'll be posting up suggestions for that one to be re-valved here later on.

This seems very helpful for both as far as I can tell:


http://www.kdxrider.net/Kayaba.htm
The base valve is the same part number on 1997 - 2004 KX500 forks. When you take it apart, be sure to flat file the peening off before taking the nut off. You will possibly break the stud off if you don't. Measure the quantity, thickness and width, then post up the numbers. I can not find the stock valving on the internet.
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KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by Chuck78 »

I definitely recall watching a YouTube video over the winter of a similar cartridge where the end was peened over and needed filed down. It was a general tutorial on cartridge forks, possibly KYB forks. I wish I remembered to save a link for that! I will search for it tonight after I get done sweating in the garage.

I will definitely measure and post the specifications of the valving that I find, as well as a picture, just in case someone finds that is not stock. Do they not list each individual valve shim washer in the parts fiches?
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KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by KDXGarage »

Chuck78 wrote:I definitely recall watching a YouTube video over the winter of a similar cartridge where the end was peened over and needed filed down. It was a general tutorial on cartridge forks, possibly KYB forks. I wish I remembered to save a link for that! I will search for it tonight after I get done sweating in the garage.

I will definitely measure and post the specifications of the valving that I find, as well as a picture, just in case someone finds that is not stock. Do they not list each individual valve shim washer in the parts fiches?
" Do they not list each individual valve shim washer in the parts fiches?"

No way.

Post a picture of the base valve before you take it apart.
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KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by Chuck78 »

Ahhh... I see. It only breaks it down to the whole cartridge valve assembly, 49116VALVE-ASSY,FORK 49116-1150 $104.90 x2




I also just noted that some parts variances between the compatible swap years, which will be good info for anyone who has found a set of 97-04 KX500 triples to use as a direct bolt-on for the 96-97 125/250 & 97-04 KX500 forks:

97-99 KX500 upper triples are a diferent part # than 2000-2004 KX500 (unsure of differences, bar mount risers?)

97-04 KX500 use the same lower triple

97-04 KX500, 96-97 KX125 & KX250 use the same lower fork tubes

97-02 KX500, 96-97 KX125 & KX250 use the same upper fork tubes (parts fiche notes Gold Anodized), different from 03-04
2003-2004 KX500 use a different part# for upper fork tubes (parts fiche notes Bronze Anodized)

97-04 KX500 use identical valving assembly part #'s for all years of this fork.

EDIT - Jason answered my question/suspicions of whether the 98 KX125/250 forks will work, as the upper triple clamp portion was the same as 96-97, & same camping diameter as the KX500 97+ etc. No, lower diameter is different. 1-off year.
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KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by Chuck78 »

I didn't bother looking it up this time, but when I bought my Fork, I also discovered that it was a much longer run of front wheels that will work. I can't remember if I cross-referenced the axle, the hub, or both, or the brake rotor additionally, but there was probably a run of 10 years or so of KX wheels that will be compatible with these forks that fit the 97-04 KX500 triples as a direct swap onto a KDX.
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Re: KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by KDXGarage »

1998 KX125 / KX250 lower clamps are larger ID than any previous year. The fork outer tubes are larger, too. They won't mix with KX500 lower clamp.

Yes. I own a set. They are not handy.
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Re: KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by Chuck78 »

I have read a couple of mentions now, one KX500 fork swapper on this forum, and another experienced tuners words, that the KX 500 piston did not flow nearly as much oil as other similar KYB fork pistons including the KX125 46mm KYB's. The one member had stated that he compared it to a YZ250 KYB assembly that he had on his shelf and the YZ piston clearly was a much better design and flowed much more oil, so he stuck that in his kx500 base valve. Apparently the piston being restrictive was responsible for a fair bit of the valving/metering traits, and putting in the YZ piston or a Race Tech piston allowed an unrestricted amount of oil to flow through the piston basically, which essentially puts all of the control in the valve shim stack tuning.

For this reason, and a 15% discount code for eBay today, I am considering just buying a Race Tech piston kit for it, also because RaceTech gives you a login code with your gold valves purchase that allows you to access their custom valving spec recommendation worksheet to get a valving stack setup tailored just for you. $118 minus 15% doesn't sound too bad to get a Race Tech gold valve compression set, that was the cheapest price on eBay.

I will post some of the last several days of dredging through 13+ years of KDXRider.net posts on KX 46mm fork valving for woods... not much info out there unfortunately, other than to remove some of the biggest compression shim stack washers.

Jason or anyone else, can you sway me towards just running the stock KYB KX500 spec guts with just a slightly softened up stack arrangement?

Thanks everyone,

Chuck
Last edited by Chuck78 on 08:52 pm Nov 01 2020, edited 1 time in total.
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Re: KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by Chuck78 »

http://www.kdxrider.net/forums/viewtopi ... ing#p49012
TopperHarley wrote:
2000 kx500 base valve shim stacks
by TopperHarley » 12:31 pm Nov 01 2007


After reading a plethera of posts about revalving the stock KX base valves, I decided to disassemble mine and see how they were stacked. I was under the assumption that they were factory stacked and had not been re-stacked. I was expecting to find a series of 12 large (24 or 22mm) shims and my intention was to remove some of them. I read a couple posts which suggested removing all but 4 of the large ones. To my suprise there were only 4 large ones in the stack. This is how they were stacked from below the valve:

4x22mm 
1x20mm
1x18mm
1x16mm
1x14mm
1x11mm clamp shim
2x18mm backer shims

I was assuming that they were revalved at some point. Funny thing about the base valves was, I still had to file down the peened stud to get everything off. I guess whoever had them apart peened them over with that tool thingy with the + or maybe just a phillips head screwdriver. No lock tite residue on threads at all.

Anybody farmiliar with a stacks like these? the first nine are like .003in thick. the last two are significantly thicker at .018".
Any input would be greatly appreciated. I am hoping that this is a woods stack and I can just put it together and ride. I did not try the forks out yet.
IdahoCharley wrote: by IdahoCharley » 09:44 pm Nov 01 2007

TopperHarley - I would just clean everything back up making sure no shims are cupped and reassemble. If you want to soften the compression up a little, remove one of the 22s. The 11 is called the clamp shim and the two thick spacers on the bottom are just that spacers (also called a backer shim or double backer in your case) basically a plate so that shims do not wear into the soft aluminum base valve and basically take-up space that would be useful to someone like Dusty Abbott (KX500 Desert Racer). 

You have a single stage stack so there is no cross-over shim. If after trying the forks on the bike and want to soften the compression dampening a little more I would remove the 20mm shim.

*******The KYB on the KX 500 and CR 500 were softened considerably after the open bike MX class disappeared. Most people buying the CR500 and KX500 were experienced trail riders and the factory made some fork valving changes to better suit the dying big bores.

*****You can not compare the stacks from your forks with the ones from even same year KX 125 and 250s. Different pistons - different intended uses. The last years of the 500s were basically just "bold new graphics" years.
TopperHarley wrote: by TopperHarley » 12:37 pm Nov 03 2007

I spoke with a suspension tuner out of illinois yesterday about my 2000 KX 500 fork valving.
He said that the base valve on these forks was very limited due to the small oil passages. He said he would reverse the valve so the larger openings would be against the shims which would alow for an effective dual stage stack to be used. He also stated that the mid valve hype was basically just a hoax and its just a fancy check valve with useless shim stacks. something about the stack being spring loaded so it just moved out of the way to allow oil to flow. Not sure if this applies to other years or not. Not sure if I should take his word for it or not. For what he would charge me, I could just buy some gold valves and install them myself. Of course, I will play with what I have and see if my arms fatigue and head falls off first. I've got to find out where they are at so I can appreciate the improvements. 
___

IdahoCharley wrote: by IdahoCharley » 04:40 pm Nov 03 2007

I think you will be surprized at how well the forks will work. The KDX is lighter bike and more lightly sprung so removing one of the 22s would have likely added to the overal bike balance. But it depends upon your terrian, speed and ability also. (I agree with Inda though in that a person always ought to have a base line on their equipment.)

The suspension tuner you talked with sent several mixed messages IMO especially on the mid-valve. Many ways to build a mid-valve - at least three come to mind - two of which do not reuse the check valve plate spring. 

Also race tech and others sell a seal grease that helps reduce stiction on standard seals and 'Synergy seals' sells seals which allow some oil residue to wet the seal. (I know this sounds like it is leaking but many people rave about the synergy seals and apparently you do not need a seal tool to install. They have their own particualar method of installation which some find easy and others struggle.)
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Re: KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by KDXGarage »

The code is good for 5 minutes. Print out every option it gives you as fast as possible.

RT is going to probably get you real close. You could test ride it, make a change, test ride it, etc. until you got it how you liked it.

If you go stock, you are going to soften it some, test ride, make a change, test ride, etc. I can give you a guess, if that is what you want.

If you want to do it one time and then just ride it however it is, then pay RT or another tuner to revalve it. If you are wanting to learn and are OK with taking it apart a few times, then do it yourself by adjusting the stock stack.

Though the majority of the damping is going to be through the base valve, don't forget the midvalve. It assists in the damping and may need to be revalved or the float amount changed.
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Re: KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by Chuck78 »

What I was looking for was the best possible performance, & also ease of tuning (only tearing it down once or twice to re-valve) is a huge bonus.

The mid valve was an entire additional area that I eas seeking assistance with. Jason, from reading many of your posts in the past dozen years, you seem to firmly stand behind keeping the midvalve and making adjustments to it. Others say mid valves are too harsh for the woods, and have no place on a woods bike.

I believe the argument there was that with the mid valve still in place, the bike is far more tunable for a wide variety of riding. Without it (with it bypassed or converted to whatever it is you do to them), the bike is more of a 1 trick pony, not very versatile in terms of being able to set it up for a broad range of terrains/riding styles.

Basically what I was getting at is that it sounded like the KX 500 piston is very restrictive and would really limit the tuning, and with a more free-flowing piston, I might be able to get better performance or a wider range of performance at least. But then again, with only 1 Spring shim washer, cartridge emulators in vintage damper rod fork bikes seem to do wonders on street bikes, and Paul Thede the founder and owner of Race Tech explains that he looked into many different methods of improving the valving of damper rod forks, and tried having a shim stack, but concluded that the cartridge emulator design with just one valve shim spring washer was the best way to go.

So yes, paying the price for the Race Tech Gold Valves would be a bit of convenience as I could get the valving right the first or second try, but the bigger thing I was getting at was that it sounds like the piston is a better design and I would be better off with it in the end as far as a further slight boost in performance of the fork. I'm not certain whether or not I could get identical performance out of the stock KX 500 piston, considering people are saying that it is far more restrictive than the KX 125 and KX 250 pistons in otherwise nearly identical forks
Last edited by Chuck78 on 09:59 pm Aug 01 2022, edited 1 time in total.
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Re: KX125 or kx500 swap - heights & valving? vs KLX300 swap

Post by Chuck78 »

I'm getting really excited now, as beyond the KX front end, Ron Black is so awesome that I just mailed payment for my 220 head machining + a new Ron Black Air Stryker quad vent carb on Thursday night, and I got a ship notification email Tuesday night that I was receiving a package from him, sent out 2-day priority!
That's some GREATservice!!!!

I have a low hours bottom end and a 0.5mm overbored, replated, ported cylinder with only a few hours on it & the Wiseco piston... I bought new rings for the piston anyway.

Fresh 220cc cylinder (0.5mm overbore = an actual 220cc, stock is 216cc if I recall?), cylinder has been ported (by CV Tech in Canada???), RB modded head, Wiseco piston, RB AirStryker Quad Vent carb...
FMF desert/rev pipe & TurbineCore2 s/a, Boyesen reeds...
Tubliss front and rear with 110/100-18 Shinko 520 rear @ 5 to 7 psi (AWESOME all around tire, especially in mud/loose/rocks/loam!), 90/100-21 "fatty" Shinko F-546 front @ 8-9 psi (also a real good tire, & CHEAP!)

The new hot rod engine will be a DRASTIC difference from the current engine whose right crank seal was damaged by blown up 220 piston, as well as the cylinder badly scored up... i threw in a Wiseco & kept riding it, while collecting these other nicer parts...

The new engine and fork will be a night & day difference (HUGE understatement)! :supz:
'97 KDX220R - purple/green! - KLX forks, Lectron, FMF, Tubliss
'99 KDX220R project - '98/'01 RM125 suspension, Titanium hardware, Lectron Billetron Pro, Tubliss
'77 Suzuki PE250 & '83 Suzuki PE175 Full Floater - restomod projects
'77 Suzuki GS750-844cc, '77 GS400/489cc & '77 GS550/740cc projects
'62 GMC 1000 Panel Truck
'88 Suzuki Samurai TDI/Toyota swaps
'88 Toyota 4x4 pickup
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