3 Different front end weights..... and stem length comparisons for KDX use!

[Chopperpilot]

Well I pulled the bikes into the garage and will soon start tearing the rear suspension apart on them. On the KDX I'm also going to look at fitting the 2003 YZ250 front end with the adapter bearing I got off amazon. I figured I'd take the bathroom scale out to the garage when I do and get weights. My plan is to assemble the front end (Fork tubes, triple trees, front wheel, tire, axle........no brakes, handle bars, or fender, etc) and weigh them as a unit and see the differences between a stock KDX, 1993 KX 250, and 2003 YZ250. I sourced wheels for the two other front ends, seemed cheaper and easier and better than trying to adapt the KDX wheel to them. Let me know if there's any particulars that you'd want weighed while I'm out there when I get them apart. Technical note: I currently have the 93 KX250 fork tubes on and they are mounted onto KLX650R triple trees. The KLX650R triples are a direct bolt on to the KDX frame (exact same bearings) and use an aluminum stem. The YZ also has a aluminum stem as expected.

[Chuck78]

I'm glad to see this info being looked into and posted! Especially the Yamaha steering stem compatibility....

I'm curious about the 91-95 KX forks weight. The lesser spec but same diameter 43 mm KLX 300 forks weigh 4.5lbs less than the stock KDX forks, so I'm wondering if those KX forks weigh roughly the same as the KLX? That's a massive weight savings. Mid-2000s Yamaha and most all other more modern Showa & KYB inverted forks are probably 3 to 4 lbs lighter with some as light as 4.5 lbs lighter, despite them being all significantly larger diameter 46-47-48mm.

The early 46mm KYB & 49mm inverted & conventional Showas ('06-ish to 2002-ish) are a 1/2lb lighter than the stock '95-'06 KDX forks. I was glad to see that until I found out how much lighter all the other forks are, I had previously assumed that larger diameter forks would be heavier than stock KDX forks! The stock KDX 43mm forks really about as heavy as it gets, and is an area where you can benefit from significant weight reduction and losing that top-heavy feel...

Now with that in mind, I'll probably be only running the 98 RM 125 conventional 49mm Twin Chamber forks on one of my two builds, because I want to get a set of newer forks and see how much lighter they are, but unfortunately that means going inverted in order to get into the ultralight forks. 2020-2023 KX450X forks are quite appealing but cost as much as a well used but running and ragged looking KDX... '05-'06 RM125 forks or really any KX250F forks 2006-2018 would be wonderful, including the SFF coil spring (non-TAC air spring) versions included.


I'm also looking at a 96-97 RM rear shock as they are 46 mm versus the '98-'04 which are 50mm like all the modern shocks, as I think the 46mm will clear the KDX crank case rear mounting a swing arm bolt better without having to grind on the cases, but the 50 mm shock is definitely a massive upgrade and gets the aging KDX up to modern specs.

[KDXGarage]

I assume that early 90's KX forks being longer than KLX300R forks would mean they weigh a little more.

[Chopperpilot]

OK, got some data today. 1st off the disclaimer...... unless whatever you're using to measure is calibrated regularly, you have no idea if it is correct! So I will tell you that I measured the 3 different front ends a lot of times each! Until I found a spot on the electronic bathroom scale I was using that I felt gave the most repeatable readings (Placing the tire on a spot roughly in the middle of the scale with the tire at a 45* angle (or pointing from lower left to upper right) on the scale. Each front end was measured assembled with tire, wheel, axle, fork tubes, triple trees with bearings, and handlebar clamps. No handlebars, fenders, brakes or number plates.
2001 KDX with slightly worn TKC 80 tire - 47.8lbs (I also got several 48.0lbs readings)
1993 KX 250 fork tubes, wheel, axle and 1993 KLX650R triple trees (aluminum stem) - 43.8lbs (MX tire)
2003 YZ 250 front end (46mm KYB fork tubes) - 42.8lbs
So there you have it. If I get done with other winter projects I could maybe be talked into taking off and weighing my 1996 KLX 650R front end (43mm USD KYBs, the R version had longer forks and adjustable compression vs the street legal version)

While I had all these front ends out and sorta assembled (the KX tubes were not fully reinserted into the KLX triples, a pretty snug fit without the triples being mounted) I thought I'd look at heights. Surprisingly both MX front ends (I measured with the tire on the floor to the top of the fork tubes) were almost exactly the same and only about an inch taller than the KDX front end. I realize that may not directly correlate with 'how much higher they make the bike', but really seemed pretty minimal to nothing.

[KDXGarage]

Thanks for the info!

[Chopperpilot]

Looking down internet rabbit holes I kept coming across 'offset clamps' for MX bikes and how great they were (22 offset!). I had assumed that they were making the forks not quite parallel with the steering head, but that's not it. They are just changing the distance from the center of the steering head (and bearings) and the center of the fork tubes. Essentially all of the aftermarket 'offset clamps' were moving the fork tubes closer to the steering head (generally from 25mm away to 22mm away). This has the effect of making the bike turn easier and be more stable (due to an increase in trail). Apparently most KTMs are somewhere around a 20mm offset. Anyhow, some YZs (particularly 4 stroke versions) had 22mm clamps from the factory. In addition, some are shorter stem length (by a few mm) than the 2 stroke YZs. When I first looked at fitting the YZ to the KDX, I noticed the bearing spacing is a few mm too long (but still workable with a washer I believe). So I think I might see about getting a set of the 22mm YZ clamps and fitting them. According to the internet the top clamp on these will need bored out 2mm (from 54 to 56mm) to work with the 2003 fork tubes, and the fork spacing on them went from 190mm to 192mm. So I'll have to space something on the wheel/axle/brake or have my front wheel 1mm off to the side! (which one person swore he couldn't notice any problem with). Anyone know for sure the offset of the KDX or KX forks? I'm guessing 25mm

[Chopperpilot]

Seller sent me an offer...... 2012 YZ450F triples are on their way. According to internet lore, slightly shorter stem, 54mm top clamp fork tube bore (needs to be 56mm for my forks), and 22mm offset (which will allegedly turn me into the IRC tire guy next time I ride!) I figured for $58 might as well see.

[Chuck78]

The triple clamp offset is only PART OF THE EQUATION... The fork tube diameter and axle lug offset is *THE OTHER* part of the OFFSET equation. rake and tore diameter/radius also are critical in this equation.

Most clamps are not striving for 22mm or 25mm offset, but vary from bike to bike based on engineers' design preferences, fork tube diameter, and head tube steering angle (aka rake aka caster). Less offset means more "trail" measurement. Larger front tire diameter (radius, actually) means more trail. Lazier steering angle means more trail distance. It's all part of a complex equation, and little bits of it cannot be taken as fact without the rest of the equation variables in mind.
More trail gives greater stability, less trail gives quicker steering as best as I understand, I believe what you wrote contradicts that slightly. Sport bikes and small race bikes have less trail, highway bikes have more trail, but off-road and MX bikes in general tend to have 4.3" to 4.6" of trail, from memory.
The KDX has a 26.5° head angle (or 63.5° depending on the terminology used measuring from horizontal or vertical), and has very skinny diameter fork tubes (43mm) for a modern bike, so the triple clamps have a greater offset if around 25mm or 28mm, I don't recall exactly but I wrote down a rough approximation when I realized the 49mm Showa RM/DRZ400 fork tubes being so much larger diameter automatically pushed the axle lug out further, which is the same as a triple clamp with a lot more offset. So of course the 96-98 RM triples have a fair bit less offset as the KDX conventionals, but the offset as a whole is similar although there's a 1/2° or 1° difference in steering angle between the two chassis. The DRZ400 triples look identical to the 96-98 RM, butbhave a different offset as they are made for mire stability for a heavier dual sport type bike, where the RM are made for rapid bursts of speed and very precise cornering...
An online rake & trail calculator is really essential in truly comparing and judging a whole setup.

Was it you that pointed out Emig or someone had a pdf chart of their triples vs the factory offsets, for all models supported? So many were in the 21mm to 23mm range, and their aftermarket "corrections" typically only varied by 1mm-2mm max.

[Chuck78]

Also, weighing the forks with a matching front wheel and axle is great, but the wheels will all be close in weight enough... It's the tires that are a huge variable, as some tires like Hoosiers and other MX tires are ultralight carcasses, while others are quite thick and rigid for off-road punishment... There can be 3-4 lbs difference in rear tire weights, probably half that for fronts due to being of more uniform widths and treads

[Chopperpilot]

Also, weighing the forks with a matching front wheel and axle is great, but the wheels will all be close in weight enough... It's the tires that are a huge variable, as some tires like Hoosiers and other MX tires are ultralight carcasses, while others are quite thick and rigid for off-road punishment... There can be 3-4 lbs difference in rear tire weights, probably half that for fronts due to being of more uniform widths and treads

True, but I wasn't going to dismount tires! That's why I listed the TKC 80 as being on the KDX wheel, as I imagine that'll be the heaviest one being dot legal.

As far as the offset clamps..... we are essentially talking apples to apples because this is coming from people who are riding the same bike and are only changing the clamp offset and are happy with the result. I will concede that some of their 'happiness' may be because they spent between $650 and $1000 on a set of aftermarket clamps and want to justify that expense, I figure I can play with it for $70 or so. Less offset creates more trail (as you stated) but also (according to reviewers) makes the slower steering lighter. This 'shouldn't' be possible, but could be explained by moving the fork tubes closer to the steering axis would lighten up the steering feel vs fork tubes further away from the steering axis. There must be something to it judging by people's reaction to it (this of course may or may not play out on the KDX frame). The other benefit of the 2012 YZ450 clamps is they have two positions to bolt bar mounts to allowing you to experiment with how that feels.

[Chuck78]

I think before jumping to conclusions, you should at least compare the rake/trail/offset of the donor bike with the KDX rake and trail in mind, so that you can see how far you're taking the trail change. Less offset than the stock donor might be a good thing as most modern MX bikes have lazier rakes around 27.5° vs the KDX being rather crisp at 26.5°. Some KX125 were 26° (KX250 usually was a half degree more slack @ 27° iirc), & I'd even seen a bike at 25.5° and reportedly quite stable despite the steep steering due to the trail balancing it out.

I'd be trying to keep it within reason but more offset is nice for oversized tanks as you can keep the fork tubes away from the tank further! Don't compromise the rake vs trail for that though unless all you do is tight technical slow trails where turning radius is critical (or learn pivot turns & slow wheelies!).

[Chopperpilot]

Well I plan on setting up both triple clamps so comparisons can be made. Pretty much everyone is reporting that the smaller offset just helps everywhere, tight turning, staying in ruts at speed, and straight line stability. Also they move the forks 1mm further out from the stem, so it remains to be seen how much tank/frame interference it would be. So for $70ish it seemed reasonable to check it out.

Some other things I've discovered and I'll post it here because I'm not sure of a better place to.
I got the 2003 YZ250 front end not because I specifically sought it out, but because it was a super good price on ebay with free shipping to Alaska. In checking various places about valving for it I discovered something about 99-03?? YZ 46mm forks. Alot of MX'rs hate them, probably why the great deal. The problem is they have a huge diameter cartridge and rebound piston (32mm) which creates a big problem trying to run a mid valve in because of the shear amount of fluid that goes through the mid-vavle. People report both blowing through the stroke and mid stroke harshness. The 2003 year was the last iteration they tried with the 32mm set up before ditching it and going with a 28mm cartridge. It seems that I lucked out again in this as the 2003 was the 'best' setting on the mid valve. This thing has a mid valve float of about 2.5mm! which is nearly check valve territory until you realize the amount of oil flowing through the big diameter piston with huge ports in it. The 2003 fork uses 2 shims on the mid valve a 27 x .30 and a 20 x .40. Apparently, earlier versions (00-02?) used less of a float (about 1.5mm or more) and more/thinner shims. These forks were known for the mid stroke harshness and bending/warping the shims to the point of damaging the shims. So I guess I would say that although it's cool I found a way to mount yamaha stems to KDXs with the adapter bearing from amazon, I wouldn't seek out a 46mm YZ set. The 48mm OC YZ forks (just before SSS) are apparently really good and easier to set up with the smaller cartridge for woods. I however am rolling full steam ahead for now because 'why not?' Many people recommend converting a mid valve to a check valve for woods anyway (I don't really agree with this, but) and this particular set up might work well as a few people claim with 46U YZ forks with the base revalving and the high float setup of the 2003 mid valve. The 93 43U KX forks have no mid valve and they function significantly better than KDX forks, so I think these forks with their mid (check) valve, might be made to work well and possibly protect against a big drop with the mid valve setup they have. It sounds like the CR and KX 46U versions maybe didn't run this 32mm setup, I'm not sure whether their triple clamps are easier or not to adapt to the KDX, but if you got a deal on the CR 46Us, they are apparently a sweet setup after you remove the bladders.

[KDXGarage]

I remember some talking about that 20 years ago. Look on ThumperTalk's suspension forum for NC Mountain Man (I think his name was) and a tuner named Dave making a clover leaf midvalve (as best I remember). That mountain man guy spent a TON of time trying to get those forks to work better for him!

[Chopperpilot]

OK another update on the YZ front end, it actually fits! I realized I'd been talking as if I had fully mounted it up to the bike, this wasn't quite true as I didn't have the correct bottom bearing on the stem (stock KDX bearing) or the adapter bearing race in the top of the frame. Well I installed both those and torqued the triple trees in (instead of loosely attaching them 'to see') and put the fork tubes and front wheel on. Like pretty much any USD setup, the triples contact the tank (in a completely different spot than the KLX/KX triples did). It looks easy enough to fabricate a 'U' shaped piece of metal to place over the factory KDX frame stop (either weld or drill a hole through it and bolt on the 'U') that will engage the YX frame stops. The stem length is pretty much perfect from what I can tell, not too long as I had originally feared when I measured it against a KDX. So perfect that I'm wondering about the 2012 clamps now because they are 4mm shorter stem. I'll let you know when they come in. Another bonus for these clamps is that they are a 54mm upper clamp diameter and a 59mm lower clamp diameter...... So sets of SSS fork tubes will slide right up in these, just watch for ones with 54mm upper clamp diameters, some have 56mm.
Oh, and Chuck78, I did end up finding a post on TT where a guy tried the later model 22.5mm offsets and went back to the 25s, he thought the 25s did better for him. I'm sure at my current level I wouldn't know, but if I progress as much this summer as last, maybe I'll be able to tell.

[Chuck78]

OK another update on the YZ front end, it actually fits!
Well I installed both those and torqued the triple trees in (instead of loosely attaching them 'to see') and put the fork tubes and front wheel on.

The stem length is pretty much perfect from what I can tell, not too long as I had originally feared when I measured it against a KDX.
So perfect that I'm wondering about the 2012 clamps now because they are 4mm shorter stem. I'll let you know when they come in.

Another bonus for these clamps is that they are a 54mm upper clamp diameter and a 59mm lower clamp diameter...... So sets of SSS fork tubes will slide right up in these, just watch for ones with 54mm upper clamp diameters, some have 56mm.

Hey, that's AWESOME to hear that the YZ triples fit with just a conversion bearing, no stem swap needed!!!!!! That's BIG news!

So from what I'm gathering, perhaps one of the best swaps possible would be a 2004-2005 YZ125/250 48mm KYB Open Chamber fork, or 2006-2011 YZ forks?
Was 2011 the last year of the longer steering stem, 2012 being the first of 4mm shorter????? I may have interpreted it that way originally, but now am figuring that the shorter stem perhaps was well prior to 2011, maybe 2005 when the first aluminum frames came out. What do you know on this subject?

Also, it would be really nice to know how the Yamaha WR250 4-stroke 2000's and 2010's models steering stems fit, if they are the same, and which years of WR used the S.S.S., as most years are KYB Open Chambers, but a few years (2 years?) I recall did in fact have the S.S.S. forks,


If there was a Yamaha KYB WR250 fork 2004+ that had triples that would bolt direct into the KDX frame, this would be an incredible combo.

I'm also seeing that 46mm KYB shocks from 1999-2005-ish KX125 are listing 448mm, 450mm, and 455mm lengths - which is comparable to the Showa 50mm shocks that I'm working with, and 46mm will likely have a 2mm clearance advantage on the springs vs the KDX crankcase swingarm pivot bolt area, so this could turn into a recipe for the ULTIMATE KYB setup for the KDX...

For the Showa stuff, when I get my wrist surgery bills paid off, I may grab a 1996-1997 KX125/KX250 46mm Showa just to see how well they fit the KDX, and if the topped out clearance to the crankcase swingarm mount bolt area is 100% clear, and if the high/low dual compression adjusters fit those as well.


Please let me know what you know on the YZ steering stem lengths, and clamping diameters still!

I do know that the YZ 4-stroke KYB forks have a different clamping diameter than the YZ 2-strokes for some odd reason, so that's the difference you were mentioning with some upper triples being 54mm and some being 56mm.
Going Yamaha KYB stuff is quite nice as Yamaha is earning some serious respect for me with their significantly well proven designs standing the test of time and being built upon, unlike KTM who had a near perfect bike engine in 2017-ish, but blew that in their subsequent redesigns and outsourcing changes, and went out to pasture because of it...and also didn't have 2006 Yamaha quality suspension until 2024...

[Chopperpilot]

OK, there's alot of 2012+ YZ clamp information out there. I don't have a good chart and I don't want to post wrong information, but here's some basics. All is allegedly!
250 2 stroke clamps have the longest stems (this is for post 2012, I'm not sure where my 2003 2 stroke 250 stems fit in this)
YZ 4 stroke stems are 5mm shorter than 250 2strokes
125 2 stroke stems are another 3mm shorter than the 4 stroke stems
(this is all from an aftermarket clamp manufacturer that responded to me)
2006+ clamps have 192mm spacing between fork legs
2005 and earlier have 190mm spacing.
Various years of post 2006 clamps (so we're talking about the SSS fork legs here) had 56 and 54mm top clamps, so make sure your fork legs match your clamps. Some years of YZ450 starting in 2012 (maybe other sizes??) had 22.5mm offset triple clamps. The rest of the YZ clamps are 25mm offset. I think YZ450s went back to 25mm offset around 2017 or something.
So yes, for ease of working on and setting up for woods riding, I'd say the 04-05 48mm OC is the best bet. It appears from my measurements that my 2003, 46mm fork leg clamps, have the exact same clamping diameters (top and bottom) as the 48mm OC or SSS fork legs. Except keep in mind, some SSS fork legs are 54mm upper diameter and some are 56mm. I'm pretty sure the earlier SSS legs are the 56mm ones, because the 2012 YZ450 clamps that I got supposedly have 54mm upper clamps.
My 2003 upper clamps are 54mm diameter and have handle bar mounts cast into the clamp. The 2012 Clamps have bolt on handle bar mounts (I'll see if the KDX mounts will fit) and also have two positions to mount the handle bars, one a little more forward than the other. I will see how odd the 2mm wider stance is with my pre 2006 front wheel and if I could just get (2) 1mm spacers and then space out the caliper if necessary to get to the rotor.
When I get the 2012 450 clamps in, I'll measure the stem and compare to my 2003 and see how they are. It's weird that the companies are only sure on 2012+ clamp stem lengths.

[Chuck78]

Apparently in 2015, the WR250F got the KYB AOS "Yamaha S.S.S." closed chamber forks that the MX models fot in 2005, granted a newer version of them, and woods valved. I wonder if a 2012+ YZ250 2-stroke triple clamp has the correct diameters? At any rate, the WR250F 48mm open chamber forks with 25mm offset triples would be a great upgrade. The 2mm wider spacing width & 2.5mm greater offset would allow a tighter turning radius lock to lock on a KDX swap, and I think the larger offset may be good for tight woods riding, although that might be a bit much, reducing the trail spec dimension quite a bit, which may be a downgrade for high speed 5th-6th gear riding

[Chuck78]

Yamaha has 3 stem lengths. Short, mid and long. The 125 and older 250f use the short the 250 and older 450f use the long and the newer 4 strokes use the mid. Mid = 0 short -5mm long +5mm.

https://www.thumpertalk.com/forums/topi ... -on-yz125/


--------------------------------------------------------------------------------

I have my pal's 2008 YZ125 here to change her fork and shock seals and I have my *2011 YZ125, both are assembled.
Measuring from the bottom of the lower clamp to the top of the stem with a stainless ruler I see 268mm on those bikes.

I have two stems in the drawer, one that I labeled with a sharpie as the original stem from my 2011 YZ125 and the other is from a set of 2008 YZ250F clamps that I put on my '19 YZ250.... Those stems measure about 267.5mm from end to end.

*Currently I have 2008 YZ250F clamps on my 2019 YZ250 and 2011 YZ125.
The 250F Aluminum frame stem is the compatible with the YZ125 aluminum frame.

The YZ250 two strokes from at least 2002 up use a longer stem.
Without disassembling my 250, I measured 275mm from the bottom of the lower clamp to the top of the stem.

Hopefully that helps. Here's a photo with some stem diameters for the 2011 YZ125 stem. The 250, 250F and 450F stems share these diameters back to at least 2002 model YZ250s and at least back to 2005 model YZ125. I bet the diameters have stayed the same since models farther back than those years, but I can't confirm it.

image-20240417221019-1.jpeg (254.48 KiB) Viewed 27558 times

https://www.vitalmx.com/forums/tech-hel ... tem-length


This also is good info as it says basically that the 2005 and newer press fit diameter is 30.15 mm, if you look at the photo and the handwritten measurements on the diameters.
--------------------------------------------------------------------------------

Here’s some more info I found on another site for anyone that stumbles across this thread in the future

***keep in mind this is older info and model years beyond 2014/2015 likely also fit this description but the newer years were omitted due to anything much later not existing at the time it was originally written***

"Looking at Applied Racing's online catalog they have the following notes:

'Short' YZ stems fit:

98-14 YZ125
98-12 YZ250F
98-09 WR250F



'Medium' YZ stems fit:

08-15 YZF450
12-15YZF250



'Long' YZ stems fit:

98-14 YZ250
98-07 YZF4XX
98-10 WR450F



I also found some notes that Yamaha changed the OD of the portion of the stem that presses into the lower clamp sometime around 04 / 05, so that's good to know.“

I got some 06 CRF250 forks for an absolute steal and I’m looking to mount them properly to my 00 YZ125, the Honda stem is just a bit too long (about 10mm) and the stem in the Terry Cable clamps is too large at the base to press into the Honda clamps

This is good info also for Honda swaps, as it states that the 2006 CRF250 steering stem is 10 mm longer than the YZ125 stem. I always suspected that the Honda steering stems looked to be longer and potentially a direct swap onto a KDX. So apparently they are just a hair shorter than the YZ250 two-stroke steering standby 2 mm or perhaps 5 mm, as I'm not sure if there is a 4 mm or a 5 mm difference in each of the short medium and long Yamaha steering stems. I also have not figured out any of the correlation to the WR250 steering stem lengths, this would be nice to know.



Granted, the critical measurement is just from the bottom of the lower bearing surface on the stem to the top of the upper bearing smooth surface on the stem, I believe these stem measurements are end to end, I'm not sure if that is from the bottom of the triple or the bottom of the lower bearing surface. These are all just guidelines and unless we have exact detailed info on how they were measured and where, then don't take it as 100% fact. It is still great info to have for reference though, especially with chopperpilot having the YZ250 & YZ250F stems sitting in front of him to give us more specific actual measurements of the bearing distance to correlate to the head tube distance on our frames
--------------------------------------------------------------------------------

I can give you the length of the long stem later today. Meanwhile, I can tell you that the mid length stem will be 5mm shorter, and the short stem about 10-12mm shorter.

--------------------------------------------------------------------------------

Visited the local dealership and got some ballpark measurements with a tape measure. (Yeah, not accurate, I know, but it's what I had.) They have a 2015 WR250 and YZ450 on the showroom floor, which based on the fitment data from Applied Racing should be a medium and long stem, respectively. 7.5" between the bearing faces roughly on the WR, touch longer on the YZ. On my antique I'm at about 7.5" as well so I suspect the medium will do the trick?

Update:
I just lucked out, I've got drawings with dimensions for YZ stems right from Applied Engineering Racing themselves, so now I can compare to my setup and select the right one.

.
-------------------------------------------------------------------------------

Tri star racing only makes 1 set for all 06-up Yz models 125-450cc. Upon measuring it has the 125/250f shorter length stem, not the 250 2 stroke/450 12 mm steering stem

.

-------------------------------------------------------------------------------

I'm looking to put SSS forks on my 2000 YZ 125. I did see the thread about someone installing 06 forks using 04 YZ450 triple clamps (after pressing and swapping stems as the 450 stem was 10mm too long). I tried using the Applied triple clamps catalog to back reference but I'm having some trouble. I'm looking at a pair of 2008 YZ250F clamps and forks in pretty good condition and was wondering what needed to be done to get this to work.

I've also read that anything later than 06-07 forks use a smaller brake caliper or something so the bottoms wont work.

the YZ250F was the first & only bike to receive the smaller front brake caliper (5XC-2580T-G0-00) in 2007. The other YZs & YZFs picked it up in 2008.

https://www.partzilla.com/product/yamah ... f401d8d63a



Also, the 250 & 450 WRs never updated, and continue to run the older (1C3-2580T-00-00) caliper. :excuseme:

https://www.partzilla.com/product/yamah ... f16414610d

^^^ https://www.thumpertalk.com/forums/topi ... -on-yz250/

So that one says that an 04 YZ 450 steering stem (listed above as a long stem like the YZ250 2-strokes) is 10 mm longer than a YZ 125 short stem.
That also shows WR250 forks through around 2008 having the short stem, but nothing on 2009 through 2014 or the WR250F S.S.S versions. I'm curious about the later WR models as that would be an excellent fork for a KDX swap, or the WR450F with a spring swap for anyone that's not a heavyweight rider. At any rate, the later wr250 forks should be able to work with a different pair of triples or another Yamaha triple clamp set as a stem donor. These swaps are great because they all have nice aluminum steering stems, and I always cringed at the fact that people would remove a nice aluminum steering stem on their fork swap and put in the heavy steel KDX steering stem. A little bit of weight savings everywhere possible yields great weight savings on an older bike like a KDX, as you can get them feeling a lot less top-heavy and handling a lot more like a modern bike or even better considering the lighter reciprocating Mass versus a 300 or any four-stroke.



Just a few posts dug up from a Google search. I may update this later, extra quotes for spaceholders.

https://www.google.com/search?q=YZ+WR+s ... ertalk.com

[brademan76]

Chopperpilot- thank you for all the research and experimentation! If this results in another simple swap option, how huge!!

For now it is difficult to follow along with all of the "I believes" and "it appears", etc. So looking forward to your hard firsthand data and results!

[Chuck78]

So from what I'm gathering above, with the conversion bearings now recently available in the last couple of years, both the long Yamaha stem found on the YZ250 2-stroke and some of the other models of 450, and probably Honda CRF250X/250R forks, the steering stems can be a direct fit now... No stem swap or knurling needed if you get the right triple clamps.
It sounds like there is a 10 mm difference between the shortest and longest of the three Yamaha stem sizes I believe (YZ125 & -'09 WR250F/-'11 or -'12 YZ250F etc)? And 10 mm difference between the YZ 125 short Yamaha stem and the CRF250. So if the YZ250 2-stroke steering stem chopperpilot has fits the KDX frame well, then we have a new standard for KYB fork swaps. I'll check a few Suzuki steering stems in the next few days for the press fit diameter, but those might also work out nicely to fit a Yamaha stem in as well, with a press fit and no knurling or bushings required! The Showa forks certainly are very nice. The 06+ KX250F & KX450 & X models used show up most years, with some years KYB I believe the early 450s and 2019 through 2023 KX250F/X.

The Hondas use Showa pretty consistently since the KYB equipped CR125 halted production, and only '96 CR250 used KYB. The CRF250 has used Showa nearly the whole time, but I believe a lot of the CRF450 models were KYB still, same as some of the KX450 years, while all but 2004-2005 and 2019-2024 KX250F were Showa, back to Showa for 2025 on the KX250X as well same as the 2019-2023/'24+ KX450/KX450X has been Showa the whole run. Interesting Honda and Kawasaki keep fairly equal business relations with BOTH Showa AND KYB at nearly all times... Showa seems to be on top again, as they were the original innovators in my eyes with the Twin Chamber forks a decade before the KYB AOS aka "Yamaha S.S.S." came out, and the 50mm shocks being standard far before KYB made the jump in size.