KDXRIDER.NET

I decided to catalog some steering stem press fit diameters for fork swap reference, for my KDX hybrid build and various KDX applications.

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TLDR summary:
'98-'06 KDX triple clamps generally have the same press fit diameter as 1998+ KYB forks' triple clamp steering stems, but Showa steering stems are generally slightly larger, which require a fair amount of knurling and retaining compound if swapping stems.

The early KDX steering stems with a smaller press fit diameter just barely over the 30 mm bearing size, I'd personally not advise trying to knurl to fit the Showa triple clamps, but it is possible to safely do this with a retaining compound made for higher clearances than the typical retaining compounds used.

The Honda CR250/CRF250/CRF450 & medium length and longer Yamaha stems out of 3 lengths are comparable to the KDX steering stem length & KX up to 2002-ish.
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I'm looking at KX125/250 & YZ250(2T) steering stem swap options into 2019+ KX450X triple clamps, for my '97 KX125 / KDX220 hybrid, as although workable (the taller stem raises handlebar height 8-10mm higher) with a spacer under the bearing preload nut in order to not run out of stem threads), the late model ('17+ or '19+?) KX stems are +8mm taller than the KDX & '92-'02 KX, & '03+ KX ('04+? or aluminum frame '06+?) are +6mm taller than the KDX & '92-'02 KX125/250 stems.


'98+ KDX steering stems seem to have a very good chance at being a press fit into mid/late-1990's to 2003 KX125/250 triples, but not KDX stems '97 & earlier.

'98-'06 KDX & KX125/250 through at least 2003 are a good press fit, 30.15mm o.d. stem press area:

strider80 wrote: 10:38 pm Aug 09 2006 2000 KDX stem into 2001 KX125 triple, no knurling.

Both stems measured 30.15mm DIA
Both triples measured 30.13mm DIA

So it is about a .02mm press fit. It took 10 tons to press out the KDX stem and 1 or 2 tons to press the KDX stem into the KX lower triple.

The '03+ KX stems are 6mm taller than the KDX & '92-'02 KX125/250, & at some point later ('17+ or by '19?) the stems grew a few millimeters additional at +8mm taller than the KDX/'92-'02 KX125/250.


Somewhere around 2004 (maybe the 2-strokes stay the same until the end in 07/'08?) or at least the 2006+ aluminum frame debut 4-stroke KX250F, the stem is again a larger press fit o.d. requiring knurling on even the larger '98+ KDX stems.
EDIT - I believe this larger press fot diameter would be the Showa KX250F stems 2006-2018, not KYB KX450F years through 2018, nor the KYB 2019-2024 KX250(F). Press fit diameter seems to be a fork/triple clamp manufacturer thing as opposed to being exclusively bike model specific. This also would seem to be the case I assume for 2019-2026+ KX450/450X & '25-'26 KX250/KX250X Showa years.
This would mean that the earlier KDX stems are not a good candidate (EDIT - for the Showa years fork swaps) although perhaps they could be knurled a bit more deeply to create more of a press fit, but that would absolutely require retaining compound in my opinion, but I would use that on any stem knurling press fit job, personally.


This one is a bit of an anomaly, his friend has a 98-06 KDX which *should* have the larger stem press fit diameter, but required knurling for a 2001 KX fork that should have been the same. Perhaps his triple clamp was swapped somewhere along the line?

plb wrote: 11:04 am Aug 15 2008 Me:
2005 KX fork on 2001 KDX need knurling.

My friend:
2001 KX fork on 2004 KDX need knurling

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mikedabike on ThumperTalk.com @ 9/2020 wrote: 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 believe the mid-length YZ steering stem can work but it's just barely tall enough for the KDX, whereas the longer YZ stem is similar to the Honda CRF stem at 2mm taller than the CRF250/450 stem and perfect for the KDX & up through 2002 KX125/250.

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cwtoyota on VitalMX.com @ 4/2024 wrote: 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.

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. This seems to be the common 1998+ KYB press fit dimension.
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Bobby Barracuda on VitalMX.com @ 4/2024 wrote:
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***

Kurlon on ThumperTalk.com in 2015 wrote: "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 YZF400/426/450
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 stem by 2mm 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.

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grayracer513 on ThumperTalk.com @ 7/2015 wrote:
I can tell you that the mid length Yamaha stem will be 5mm shorter, and the short stem about 10-12mm shorter.

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M3t on ThumperTalk.com @ 9/2018 wrote:
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.

ThumperTalk wrote: the YZ250F was the first 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 ... 580T-G0-00

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

https://www.partzilla.com/product/yamah ... 580T-00-00

^^^ 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.





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On a side note, for these 2019+ KX450 Showa 49mm forks, for my '94-'02 KX125/KDX220 hybrid build frame, I was considering going with the 23.5mm offset CRF450RX triples for the extra 0.50mm offset and the proper height steering stem, but for some reason besides OEM '15 & earlier RM-Z & RM + steel frame YZ (lower?) OEM bearings, a KX125/250 steel frame to 30mm steering stem conversion bearing is not a very common size although Yamaha has them for a good price. 30x52x16. AllBalls also lists 30x52x17 for the same applications, but that also is not a common size, even lesser so. It is available though.
This made me want to go with a very common 28x52x16 for the KX/KDX hybrid build if possible, basically meaning I need to find a press fit stem swap from a mid-'90's - 2002 KX or a YZ250 2-stroke or YZ250F mid-length-years stem, if the press fit diameter works out.

Take note that for the KDX frame, for a 28 mm upper stem bearing diameter fork swap (to fit the medium and long length YZ/WR stems/triples and Honda CR / CRF triples to the KDX), the 28x47x15 bearing size required is an abnormal size, which is not an industry standard size whatsoever, but just in the past year or so, generic bearings of this size that work perfectly for our KDX fork swaps to KX or YZ/WR forks, now are available on Amazon and eBay and other similar sources, although they are generics from China, I haven't read of any problems with their quality yet. It is a steering stem bearing and not a wheel bearing, not something subject to high RPMs...
One last thing about that generic non-standard bearing swap size, if you go up just 1 mm larger diameter in the outer bearing race O.D., 28x48x15 vs the necessary 28x47x15, the 48mm O.D. version is in fact an industry standard size. I often wondered what the architecture of the bearings would be, if you could simply use the OEM KDX outer race on the upper bearing with a name brand 28x48x15 roller bearing...????

Here's a bunch more info dumping from a previous discussion of mine with chopperpilot:

Apparently older Honda CR125 stems are roughly 14mm shorter than CRF steering stems, so I'm reading ('91 CR125 vs 2005 CRF250X).

Another recent thread on here titled KYB AOS Forks states that the steering stem was the perfect height for the KDX frame, at least for this rider's '09-'12 CRF450R triple clamps.

So the modern CRF250/450 forks' triples will be good fork swap candidates, KYB & Showas, as well as YZ250 2-strokes and *maybe* the 2012+ 4-stroke YZ triples? Even in the case of different clamping diameters, say maybe a KX250F SFF coil spring non-TAC fork is different than the dual spring Showas used on all Hondas and some KX-F's, perhaps these Honda & the long Yamaha YZ version stems will be swappable to the KDX frame? With luck

I did read that 2017 the KX steering stems got about 3mm longer than 2003(?)-2016. That tells me that the 2003-2016 stems should be pretty workable on the KDX.

The CRF250X forks would make a nice basis for a swap for sure. The compression adjuster on the CRF250R models apparently has an additional shim stack just for it, and I'd read of suspension tuner converting that simply to a check valve setup to get it closer to 250X spec for woods riding...?
The CRF250 offset was shortened for handling design changes in 2008. The fork lug offset was changed -0.50mm on the 2008 R and X, and the remainder of the 2mm reduction was in the 2008 CRF250R/X triple clamps.

Updated info from ThumperTalk CR fork upgrade for XR400R's & other Hondas wrote:
Will the bearings be in the right location on the stem and in the neck?

The CRF250/450 stem spaces the upper and lower bearings about 180mm(?) apart vs 145mm for the 230F

(I believe this "about 180mm apart" is referring to bottom of lower bearing to bottom of upper bearing stem area, which in this CAD drawing is 177.30mm according to the guy posting this on TT)
Also of note, the CR125 steering stem that was too short by a around 14mm was a 1992, perhaps the newer versions got longer like this CR250R stem, or perhaps the CR125 is like the YZ125 and uses a shorter steering stem than the bigger version 250 bikes?

This 2000 CR250 steering stem drawing shows dimensions which are very helpful, 191mm spacing from bottom of lower bearing to top of upper bearing surfaces, this could work just as well or better than the medium length or long Yamaha stems! I believe around 190mm bearing spacing was perfect to me for the KDX frame when sizing up the VStrom DL100 stem I have here (190mm bearing height bottom to top) for my '98 RM125 triples


It seems that a pair of revalved '04-'17 CRF250X or 2018+ CRF250RX forks would be a really good candidate to run if the CRF250 steering stem is long enough the way the KYB CRF450 stem is from earlier models in the 2000s. Or those triples with 2006-2010-ish KX250F forks likely have the same clamping diameters although not confirmed yet, but they're both 47mm Showa Twin Chamber inverted forks.
The 2021+ KX450X Showa Twin Chamber 49mm inverted forks (or 2017+ CRF450X / CRF450RX forks and triples - better KDX fit and better axle lugs for rotor guard mounting) could truly be the ultimate, with some downrated springs mind you, they, down as low as .38kg/mm from Eibach, but the steering stem is 8mm longer but workable - perhaps the 2020's CRF version of those 49mm Showa forks' triple clamps might have a better stem length and a 30mm i.d. upper bearing? Edit - I've picked up a set of 2024 KX450X forks (VERY NICE - new Babbit's pro race team takeoffs from Lyndon Snodgrass & teammate) & 2019+ KX450 triples... Workable for sure and 23mm offset,
However, I may look at a 2017+ CRF450 triple clamp set for 22mm offset and a better KDX fit steering stem.
CRF450 49mm Showa clamping diameters are right on 2019+ KX Showas, 53.9mm upper, 59.3mm lower - although the CRF are 192mm width spacing vs the KX 190mm, so some custom spacing may be necessary.





I found a source for at least the fork clamping diameters, my favorite place to buy parts off ebay new and used, OEM Cycle, although they don't list too much in the way of modern bikes unfortunately, and seem very biased towards the MX versions only.
Just go to the engine and parts ID information page and scroll to the right quite a long ways until you get to the fork info.

https://oem-cycle.com/BikeIdentification.shtml

here's some limited info on fork clamping diameters, not all years are documented, hence the erratic or narrow time frame windows:

2006-2012(+ to 2018?) KX250F Showa Twin Chamber 47mm forks -
clamping diameters: UPPER 52.7MM - LOWER 58.4MM

2004-2007(+) CRF250R/CRF450R Showa forks -
clamping diameters: UPPER 52.8MM LOWER 58.4MM (probably the same as the Kawasaki KX-F versions, measured at a different time on different calipers or caliper calibration.)

1998-2004 YZ250 2-stroke KYB forks -
clamping diameters: UPPER 53.9MM LOWER 58.4MM

@KDX Garage,

Do you recall exactly when the KX steering stem height increased? Was it 2003? Or beginning with the aluminum frame 2006 KX250F?

Do you recall if any of those later 2-strokes or the first of the 4-strokes ('04-'05 KX250F/ '04-'06 RM-Z 250) used a straight diameter on the press fit portion with a retaining circlip groove cut into it instead of the stepped flanged larger OD end on the steering stem as the retainer to prevent it from pulling through?
The 2020 KX250(F) KYB stem's press fit diameter was in fact the same as the 1990's 2000's (KYB) KX125/250 triples though, 30.15mm or 30.16mm, as well as the same as the '98-'06 KDX's.




This 2020 KX250(F) triple I just pressed apart had this retaining clip construction. If running the flanged type stem vs the circlip type, I'd have to bore the triple slightly larger or turn down the flanged end slightly to make the stepped flange o.d. just a hair smaller. I see in the photo above that the KYB YZ fork'd triple clamps also use the retaining clip style, ***which are also 30.15mm press fit.***
Perhaps it's time I need to choose between a medium vs long YZ stem if the KX doesn't pan out, although I could use the KYB years CRF450 stems (2009-2016) if I want to use the not as common 30x52x16 bearing size on the upper position (uncommon but used on steel frame YZ models and '15 & earlier RM-Z & RM). I'd initially started this search because the 28x52x16 bearings are very common.
^^^^^ I'm now seeing the otherwise identical appearing 2019+ Showa KX450 triple clamps use the flange style stem retaining stop vs the circlip, so this does seem to be a newer KYB vs all Showa type difference, AND it does seem that the triple clamp is specific to the fork manufacturer Showa vs KYB, even when the external appearance and clamping diameters are virtually identical.

The retaining clip style to me very much appears to be a manufacturing streamlining design and nothing else, as they can use a smaller diameter piece of bar stock to machine the stems out of, versus having more machining of the diameter to do for the rest of the length beyond the step on the flanged type.

The 2019-2024 KX250(F) (KYB) triples vs the 2019-2026+ KX450 (Showa) triples also have different part numbers, and now I see why.

I'm curious if the identical appearing same years KX450 (Showa) triple clamp uses a different press fit diameter than it's adjacent KYB counterpart...???


I didn't get to press out the CRF450RX steering stem tonight, rather unfortunately, as when I just started getting pressure on it, my homemade shop press' Enerpac RC106 10-ton hydraulic ram blew a seal after 20 years of my use, + it's prior life, as I'd bought used from an auction of used industrial supplies from a NASA facility! I guess it's had a good run... I really should get a pressure gauge to install on the hydraulic line if I rebuild this, it DOES say 10,000psi max on it.

2003 was the first year of the 6mm taller stem.

I don't know when the stepped bottom came around.

1996 - 1997 KDX was a little smaller diameter than 1998+ KDX stems (around 7 thousandths I think)

1996 KX125 / KX250 stem is a good bit bigger. I would not buy a set of 1996 clamps to put a KDX stem in!