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

[Chuck78]

@chopperpilot - so you have YZ250 triples from 2003, which should be a pretty standard steering stem height across all two stroke 250s and some of the 450s, would you say that steering stem is a perfect height for the kdx? Would anything shorter work still? Like the middle length of Yamaha stems? It sounds like the YZ250 2-stroke and some 450 triple clamps will bolt straight into a KDX frame for KYB, and most Honda CRF for Showa forks, is what I gather from this endeavor. You might want to change the title of the first post to front end weights and steering stem lengths for search purposes.

[Chopperpilot]

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!

No worries. So known first hand, 2003 YZ250 clamps/forks are a bolt on with a KDX lower stem bearing and an adapter top bearing (28 x 47 IIRC) available on Amazon. Fork stops need to be fabbed to prevent the top tree from hitting the gas tank. When I get the 2012 YZ450 clamps in, I can measure the length and see if they will work. I had originally thought that the 2003 YZ250 stem would be a touch too long and I'd need a washer to take up some space, but that turned out not to be true, it's exactly the right length with the bearings and races installed. I'm curious what 5mm less would do, if it would be a big deal or not. I think the 2012 YZ 450 stem is 'supposed' to be shorter than my 2003 stem.

Won't be able to ride until May/June....... so don't wait on me to get a better set of forks on.

[Chuck78]

Please let us know how that Yamaha medium length YZ450 steering stem looks to fit the KDX, that would be great info to know.

Exactly how well did the longer YZ250 2-stroke stem fit? Could it have been 4 mm shorter and still worked? This would be good info to know for interchange. I would imagine you needed a 3 mm spacer on top of the 12 mm tall upper conversion bearing, to put it level or flush with the head tube of the KDX, just to get the threaded nut clamping down on the bearing? That may be required only with the shorter stem as well, however the threads would go down deeper into the void left by running a shorter upper bearing on the 450 steering stem I presume. It would be nice to have a sketch of the dimensions of each of the steering stems as installed in the triples if you have time to sketch that out or draw them in marker on the parts, with arrows indicating distances to certain points & diameters.
Thanks again for researching these alternative routes to stem swapping, because in aluminum stem without any swap labor required is a win-win, lighter and cheaper and easier.

[Chuck78]

Apparently older Honda CR125 stems are roughly 14mm shorter than CRF steering stems, so I'm reading ('91 CR125 vs 2005 CRF250X). Not much time to look into this today though, but I opened a few browser tabs of search results from ThumperTalk.com to scan through later.

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 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.

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

crstem.jpg.d249d0f33101f731bbad736159df43c8.jpg (40.35 KiB) Viewed 28307 times

(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


I'm thinking 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) would truly be the ultimate, with some downrated springs mind you, they, down as low as .38kg/mm from Eibach, but the steering stem is 6mm 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, 23.9mm upper, 59.3mm lower - although the CRF are 192mm width spacing vs the KX 190mm, so some custom spacing may be necessary.

It would be nice to start cataloging the press fit diameters of different steering stems that are the correct length for our bikes as well. Pressing a stem out and machining a simple bushing for the upper triple isn't too bad, although anything larger I could turn down in my lathe if needed for my personal use but it would be nice to find some that are a direct swap.
Now although the RM-Z450 uses the same model Showa 49mm Twin Chamber forks, but the upper triple clamp is 1mm larger clamping diameter than the others, so the RMZ450 forks must remain with the RMZ450 triple clamps, or at least the upper triple.


So those would be a great upgrade as well, or could pretty likely clamp in a pair of KX450X forks direct into a KDX frame if the steering stem is still the correct length. All you'd have to do is have an eBay seller measure the triple clamp steering stem from the bottom of the lower bearing to the top of the upper bearing area just at the edge of the threads.

I was trying to find a 2018 Applied Racing catalog for triple clamp for clamping diameters and possibly steering stem heights, but apparently the owner passed away in 2021, RIP, and they are out of business now.

I found an alternate 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


Steering stem length is not documented as well and is pretty sporadic when doing Google searches, but Thumper Talk and Vital MX certainly seem to have the biggest hits for anything off-road suspension related. Especially Thumper Talk for valving info.

A note that I took off of Thumper Talk from our very own KDX Garage, was that the 2006 and later KX250F triple clamps have a steering stem that is 6 mm taller (Edit - taller than the YZ125 2-stroke and some older YZ250F), which I believe he had mentioned on here before as well, and noted that some or most of the KX250F triple clamps have the steering stop arrangement on the back of the triples as it stops against the frame, instead of on the front of the head tube. So these Honda CRF250X forks and triples might be quite viable. The X model forks are set up a little bit differently and generally softer for woods although they still need revalving to be compliant and plush amongst the rocky rooty trails, what people refer to as "trail trash" which will deflect even the 250X models.

[Chopperpilot]

Ok, got the 2012 YZ450F triple clamps in today. They are a little shorter than the 2003 YZ250 stem but I think it'll still work. The factory Yamaha bottom bearing is smaller than the KDX bottom bearing, so I put the 2012 clamps in the frame using the upper adapter bearing and they fit 'perfect'. I think with the KDX bottom bearing (which I'll get another one now that I know it 'should' work) it won't suck up into the frame as far, this is what happened with the 2003 stem. I'm thinking there will still be plenty of threads and top bearing surface engaged to work. The 2012 and 2003 clamps both use 54mm upper clamp diameters and 59mm lower clamp diameters and fabricating a stop for one should work perfect on the other as the triple clamps hit the tank in the same spot about the same distance from engaging the frame stop (which they'd actually miss the frame stop under it).
The 2012s have bolt on handle bar clamps (missing on mine) and the KDX bar clamps are a touch too thick to fit in the holes, but tempting to ream them out to accept the KDX clamps (without the rubber bumpers though). The 2012 have 2 positions to mount the bar clamps which is pretty cool to experiment with. Also nice now that I can easily swap a set of 25mm or 22.5mm offset clamps to see how that affects handling/riding.
I'm pretty sure the 2012 clamps have a slightly different fender mount spacing....... which happens to work out because when I first got a fender for the YZ front end I ordered the wrong one and I'm pretty sure it'll fit these clamps! (if only I could get it in green!)

[Chuck78]

Ok, got the 2012 YZ450F triple clamps in today. They are a little shorter than the 2003 YZ250 stem but I think it'll still work.

The factory Yamaha bottom bearing is smaller than the KDX bottom bearing, so I put the 2012 clamps in the frame using the upper adapter bearing and they fit 'perfect'.

I think with the KDX bottom bearing (which I'll get another one now that I know it 'should' work) it won't suck up into the frame as far, this is what happened with the 2003 stem.

I'm thinking there will still be plenty of threads and top bearing surface engaged to work.

Ahhhh... So the YZ250 2-stroke stem fitment was with a smaller o.d. lower bearing, so the stem was sitting up higher in the frame?
This would make the middle length Yamaha stem a bit more of a stretch for fitment, right?
Can you measure and post the lengths of the steering stems from the bottom of the lower bearing surface to the top of the upper bearing surface where the threads start / bearing surface stops???

I'd like to have some hard data on fitment on these two lengths of stems if you can get that data for us.

Thanks for this endeavor!

[Chopperpilot]

Yes, I will get some measurements (with a tape) and convert to mm. I think the middle length stem will still work fine, I think the short length stem probably would not.

[Chopperpilot]

OK here's the stem measurements taken from under the bottom stem bearing to the top, and to the threaded portion of the stem above the top stem bearing surface.
2003 YZ 250 -247.65mm total length 193.675mm to the threads for the upper bearing

2012 YZ 450F - 242.8mm total and 190.5mm to the threads for the upper bearing

So these correlate to the aftermarket triple clamp manufacturer saying that the 4 stroke stems were 4mm shorter than the 2 stroke 250 stems. The adapter bearing is 15mm thick (measured, despite I think it was advertised as a 12mm thick bearing). I just went and mounted the 2003 bottom clamp into the frame with no upper seals/dust covers. The long 2 stroke 250 YZ stem does appear to be the 'perfect' height. The top bearing (when stem is 'torqued' down and starting to create steering drag) sits just a smidge below the threads (somewhere between .5 and .8 mm). So my guess is the 4 stroke (or medium) YZ stem length will have the top bearing just starting to intrude into the thread area. I'll verify when I get another KDX bearing set in. Right now I'm planning to run the shorter 2012 clamps for the multiple handle bar position mounting and the lower offset, I'm not concerned if the upper bearing slightly intrudes into the threaded area. But if you are looking for clamps, go for the 2 stroke 250 clamps with the longer stem.

[Chopperpilot]

Ahhhh... So the YZ250 2-stroke stem fitment was with a smaller o.d. lower bearing, so the stem was sitting up higher in the frame?
This would make the middle length Yamaha stem a bit more of a stretch for fitment, right?
Can you measure and post the lengths of the steering stems from the bottom of the lower bearing surface to the top of the upper bearing surface where the threads start / bearing surface stops???

I'd like to have some hard data on fitment on these two lengths of stems if you can get that data for us.

Thanks for this endeavor!

No, I fit in the 250 2 stroke clamps with the correct bearings for the KDX frame and it fits 'perfect'.

Judging by the clamping diameters you listed for the CRF forks.... I'm certain you could just use the 2 stroke 250 YZ triples and those fork legs (YZ has a 54mm upper clamp diameter and a 59mm lower clamp diameter). Worst case you might have to ream the lower clamps a touch, but you know the stem will be dead nuts on.

[Chuck78]

2003 YZ 250 - 193.675mm to the bottom of the threads for the upper bearing

2012 YZ 450F - 190.5mm to the bottom of the threads for the upper bearing

So...the 4 stroke stems were 4mm shorter than the 2 stroke 250 stems.

The adapter bearing is 15mm thick (measured, despite I think it was advertised as a 12mm thick bearing).

The long 2 stroke 250 YZ stem does appear to be the 'perfect' height. The top bearing (when stem is 'torqued' down and starting to create steering drag) sits just a smidge below the threads (somewhere between .5 and .8 mm).

So my guess is the 4 stroke (or medium) YZ stem length will have the top bearing just starting to intrude into the thread area. I'll verify when I get another KDX bearing set in.

Right now I'm planning to run the shorter 2012 clamps for the multiple handle bar position mounting and the lower offset, I'm not concerned if the upper bearing slightly intrudes into the threaded area. But if you are looking for clamps, go for the 2 stroke 250 clamps with the longer stem.

I fit in the 250 2 stroke clamps with the correct bearings for the KDX frame and it fits 'perfect'.

Judging by the clamping diameters you listed for the CRF forks.... I'm certain you could just use the 2 stroke 250 YZ triples and those fork legs (YZ has a 54mm upper clamp diameter and a 59mm lower clamp diameter). Worst case you might have to ream the lower clamps a touch, but you know the stem will be dead nuts on.

WOW, THIS IS GREAT INFO!

So the long YZ250 2-stroke stem installed in the KDX frame has the upper bearing entirely on the smooth upper bearing steering stem surface, and none protruding into the threads at all, and sits just a hair below the threads? Does the steering stem nut then have an enlarged counterbored area to go down over the non-threaded portion slightly, in order to mate up to the bearing and preload it properly? Or is there a toothed washer with a slotted/notched steering stem for it to engage into? Or an upper dust seal that makes up some added thickness?

I really like the Suzuki stem I have here, not sure if it was a GSXR or VStrom DL1000, but it has a slot cut in the stem, and a locking washer with a tooth that locks into the steering stem vertical slot, and TWO aluminum bearing preload nuts so that you can lock them down tight together. Having just one steering stem bearing preload nut always seems like a bad idea to me....

The Honda CRF steering stems use a 30mm stem diameter on both upper and lower bearings like the Suzuki RM and DRZ400 steering stems and the street bike / ADV bike stems mentioned, so I may try to run that setup and run the two thinner bearing preload lock nuts and even slot the stem for a toothed lockwasher perhaps.

I'll have to look up all those triple clamp fork tube clamping diameters and see if they are all compatible, but that would be wild if the KYB YZ250 2-stroke S.S.S. forks had the same clamping diameter as the Showa Twin Chamber 47mm forks! I'll browse some eBay listings and see what the stem locknut situation is on the CRF250 vs YZ250 setups as well.

I'm very excited that we've made these discoveries on the steering stem lengths and available conversion bearing sizes that previously were not available several years ago. This REALLY takes KDX fork swaps to a new level that was much needed now that Ron Black is fully retired and no longer is doing his steering stem swaps and machined bushings as well as axle adapters, and sadly no KDX220 head work from the master himself RB... This will really open things up, especially if these fork clamping diameters are somewhat standard to even allow a KYB AOS Yamaha 2-stroke S.S.S. fork's triple clamp work on a Showa 47mm Twin Chamber!




Although I am absolutely in love with the 49mm Showa Twin Chamber right side up 1998 RM125/RM250 forks, they are *only* 1/2 lb lighter than stock KDX 1988-technology 43mm boat anchor forks, and the RM 49mm Showas are typical for a 1996 - early-2000's fork weight - whereas around 2004/2006+, most forks got about 3.7lbs - 4.5lbs *lighter* than the stock KDX forks - so I'm really considering going back to the inverted side for 1 of my 2 KDX220's to see what the weight savings feels like once I get both bikes fully operational (1 is in need of a TOTAL rebuild for 4.5+ years now and awaiting me to have time freed up). The CRF250X forks 2008+ sound like an excellent starting point but still need revalving despite being an "off-road" trail bike model if you really want a compliant plush woods suspension for rocky terrain. Or 2005-2006 RM125 forks, or 2009-2010 KX250F forks (2006-2008 would do as well same as the RM and CRF versions, but these got a few upgrades including some titanium nitride coatings for friction reduction 2009-2010 KX250F. All are Showa 47mm Twin Chamber forks.
For these reasons, I really feel like a Honda XR400R / 97-99 Suzuki DR350 Showa 43mm right side up fork swap is a pretty fantastic upgrade to shed weight and retain a right side up fork, as well as RMX250 46mm right side up versions of the same (triple clamp machining and steering stem swap needed on the RX versions, inverted were 91-94/95, right side up were 95-ish-99-ish end of the series)

[Chopperpilot]

Correct, the long YZ stem (2 stroke 250s only, apparently) has the upper adapter bearing just a smidge below the threads when torqued into the KDX frame enough to already cause steering drag. So yes, I would assume that the upper bearing nut does/can protrude slightly past the threads. Also this was with the bearing only, no dust seal which would definitely take up the space from bearing surface to threads.

[Chuck78]

Browsing a bit I noticed most all of these more modern bikes have a motocross rake and trail of 27.5 degrees and 4.7"-4.8" trail. The KDX has a 26.5 degree rake and I believe 4.3" trail. The combined offset of the fork lugs and triple clamps should equate to around the same as the stock KDX in order to retain this geometry. More offset and the steering might get twitchy, less offset than stock and the steering might get a bit slower. I think it will be pretty close in the ballpark if 27.5 degrees rake on the donor bike yields 4.8" trail, but I'd have to use a rake and trail calculator online and plug in some numbers. It'l give more trail than the stock KDX had, most definitely, but not as much as the modern lazy steering bike trend. 27 degrees is the max for steering angle for me, I prefer 26.5 of the KDX quite well, 27 is workable, 26 is also quite workable.

I'm curious about the 2019+ KX450 Showa and KX250 KYB forks, particularly the off-road version 2021+ KX450X Showa 49mm forks, although the price is quite high being used late model forks...
I've asked an eBay seller to measure the steering stem length between the outer ends of the lower bearing vs upper bearing @ threads, out of curiousity...He's getting back to me shortly, quick service! I believe I can get the appropriate .38kg springs for those forks from RaceTech. The CRF250RX probably has the same forks I'd imagine, listed also as 49mm Showa Twin Chamber inverted. Those have pretty heavy springs still, not anything near the rates I'd need on the KDX @ 155lbs-ish +/- rider weight. 4 strokes are still heavier than 2-smokers for the most part, although the mass is located lower for a "lighter feel."

Older forks always pose a risk of having less than desirable chrome tube condition, which is a big deal breaker, and is tough to inspect adequately when buying off eBay photos and the scrutiny or lack thereof from random eBay sellers. The 2009-2010 KX250F forks or really any Honda CRF250X/250RX Showa forks would be an excellent upgrade if I could find some in pristine condition...

The KYB Yamaha YZ250 triple clamps aren't close enough for the 47mm Showa Twin Chamber forks, although they could be used for the 2019+ Showa KX450/450X forks with machining, but I'd prefer a steering stem swap over boring the triples.


Oh...another tidbit that I'd read and forgotten, but just recalled - I believe on one of the newer KX250X model years, (Edit - it's 2024+ KX450 & KX250 models + the new KX300X/KDX300R upcoming, 32mm shorter shock according to the Dirt Bike Test review article of the '24) I'd read they shortened the shock considerably due to the fuel pump location or something fuel injection related???? I can't recall the exact details or year, or model, but I believe it was the KX250X I was reading about.

[Chuck78]

I'm curious about the 2019-2023 KX450X Showa 49mm forks now, although the price is quite high for used late model forks...
I've asked an eBay seller to measure the KX450X steering stem length between the outer ends of the lower bearing vs upper bearing @ threads, as I have a suspicion this could potentially work out really well with a spring swap and upper adapter bearing

I can get the appropriate .38kg springs for those forks from RaceTech. The CRF250RX probably has the same forks I'd imagine, listed also as 49mm Showa Twin Chamber inverted.

Older forks always pose a risk of having less than desirable chrome tube condition, which is a big deal breaker, and is tough to inspect adequately when buying off eBay.

Well... Whaddya know?!?!
7-9/16" = 192mm!!!!

Screenshot_20250202-150620~3.png (1.05 MiB) Viewed 26470 times

2019+ KX450 MX & KX450X off-road GNCC enduro racer forks could be a really good swap here!
The spring rates would only suit the heaviest of riders on a KDX being about 25 lbs lighter than the 450 that is sprung for heavier Motocross and GNCC racers, but Race Tech makes down to a 0.38 kg/mm fork spring for them! $149.99 but it is available!

Screenshot_20250202-150419.png (1.19 MiB) Viewed 26470 times

Screenshot_20250202-150516.png (1.07 MiB) Viewed 26470 times

2003 YZ 250 - 193.675mm to the bottom of the threads for the upper bearing

2012 YZ 450F - 190.5mm to the bottom of the threads for the upper bearing

So...the 4 stroke stems were 4mm shorter than the 2 stroke 250 stems.

The long 2 stroke 250 YZ stem does appear to be the 'perfect' height. The top bearing (when stem is 'torqued' down and starting to create steering drag) sits just a smidge below the threads (somewhere between .5 and .8 mm).

So my guess is the 4 stroke (or medium) YZ stem length will have the top bearing just starting to intrude into the thread area. I'll verify when I get another KDX bearing set in.

[Chopperpilot]

Those are a 30mm upper bearing though correct? Is there a 30 x 47 bearing available? Also shocking, but not surprising, that those triples look very much like the 2012 YZ 450 triples.

[Chuck78]

Those are a 30mm upper bearing though correct? Is there a 30 x 47 bearing available? Also shocking, but not surprising, that those triples look very much like the 2012 YZ 450 triples.

Actually when I looked it up I was surprised to find that the newer 2019+ KX uses a 28 mm ID upper bearing. Looking at the All Balls conversion system, they do not have a 28mm ID x 47mm OD bearing, but I do find them on the internet. All Balls DOES sell a standard 30x47x12 bearing, which could have a reducing spacer 1 mm thick (2mm smaller inside diameter) fabricated on a lathe fairly easily to fit a 28mm stem with a 3mm bearing, if the 28mm x 47mm bearings were not of high quality.


The valving on the 450X model sounds like it does pretty well in the woods, although slight adjustments may be needed for some riders to go more plush for slower technical terrain or more firm for the GNCC enduro racer types. The spring rates are very stiff though, being on a heavier 450. Race Tech and Diverse Spring both make springs down to .38kg/mm (Race Tech) & .40kg/mm (Diverse Spring in their ultralight silicon-chrome steel fork spring series).

I will buy a set of those triple clamps and see how they can fit up first before buying forks + springs & new SKF seals.
From what I'm reading, the KX450 factory triple clamps have a 23mm offset, and ride engineering offer a 22mm offset as well as a 21.5 mm, but mostly recommend the 22 mm offset and dropping the triple clamps down on the fork tubes with 3mm to 5mm of fork above the triples. 27.6° rake / 4.7" trail stock, from a quick search. tjhat'd be something like 27.4° and 4.65" trail with the triples dropped lower aka "slide the forks up in the clamps." The 22mm clamps with the fork leg offset of the monstrous 49mm forks, on a 26.5° steering angle KDX chassis, could definitely benefit from the 22mm offset clamps if running stock 80/100-21 or similar height wider 90/90-21 front tire, but I would definitely try the 23mm first - as this seems to work out better for the 90/100-21 Fatty Cheater tires I like that hard enduro and singletrack riders often run.

[Chuck78]

EDIT - I'd measured incorrectly late night initially, 38.75mm fork lug offset was grossly incorrect, disregard the numbers below until I have time to go back and edit this, but it turns out the stock '19+ KX450 23mm triple clamp offset is perfect, 34mm fork lug offset on these new 49mm Showas, SAME as stock KDX from my quick rough measurements of the stock forks and triples, stock KDX triples look to be 25mm offset approximately, I need to revisit those both with more scrutiny, but the 23mm offset is definitely what I'd want for the 90/100-21 Fatty Cheater front tires, the 22mm offset may be great for stock 80/100-21 front tires though




So I did some calculating on the rake and trail specs with the KX450X triples (23mm offset stock, 22mm aftermarket, 21.5mm aftermarket (less recommended).
I did some pretty scrutinous guesswork on the fork lug offset, knowing the fork tubes are 49mm (49 ÷ 2 = 24.5mm) + 22mm axle diameter (22 ÷ 2 = 11mm) = 35.5mm ; and then using some guesswork from ebay photos UPDATE - Forks in hand, 38mm lug offset, and we have approximately:
38.785mm fork lug offset + 23mm triple clamp offset = 61.75mm offset total / 2.43" offset total
23.0mm offset '19-'25 KX450 triples + 38.75mm fork lug offset = 61.75mm / 2.43" (OEM Kawasaki)
22.0mm offset '19-'25 KX450 triples + 38.75mm fork lug offset = 60.75mm / 2.39" (aftermarket KX / OEM Honda)
21.5mm offset '19-'25 KX450 triples + 38.75mm fork lug offset = 60.25mm / 2.37" (aftermarket)

With my preference of 90/100-21 Shinko 216MX Fatty Cheater tires at 28.07" diameter (vs 27.34" for stock 80/100-21), and the KDX's steering angle of 26.5°, This works out very similar to a stock KDX!


modern 300cc etc woods bikes got lazier with 27° and 27.5°, 4.6"-4.7" trail, and wheelbases a couple inches longer than the KDX and 94-02 KX125. I prefer the KDX/KX125 specs much better for all but steep technical slower hill climbs. I'm going to start running my chain longer / axle more rearward to help on those steep technical climbs.

stock 1995-2006 KDX 's = 4.3" trail & 26.5° steering rake angle
stock 1994-2002 KX125 = 4.3" trail & 26.0° steering rake angle


23.0mm OEM '19+ KX450 triples on KDX220R w/ 80/100-21 tire = 4.10" trail (a bit too low on trail for high speeds)
23.0mm OEM '19+ KX450 triples on KDX220R w/ 90/100-21 tire = 4.26 trail (just enough!)
(the higher triple clamp offset, the greater steering angle I can have on tight maneuvers as fork tubes will be held further from the fuel tank / frame cradle, so this is a good thing for Fatty Cheater tire users!)

22.0mm aftermarket or CRF triples on KDX220R w/ 80/100-21 tire = 4.13" trail (a bit too low on trail for high speeds)
22.0mm OEM '19+ KX450 triples on KDX220R w/ 90/100-21 fat tire = 4.31 trail (near perfect)

21.5mm aftermarket triples on KDX220R w/ 80/100-21 tire = 4.16" trail (a bit low for high speeds but workable)
21.5mm aftermarket triples on KDX220R w/ 90/100-21 fat tire = 4.33" trail (still near perfect)

This tells me that those 2009+ or 2008+ Honda CRF250/450 forks with the lugs 0.50mm closer to the fork tube centers are definitely something that is in order if you want higher speed stability in conjunction with the 22mm offset triples and the large modern diameter forks... BUT... without the 90/100-21 Fatty Cheater type front tires,
A good workaround here for 80/100-21 and 90/90-21 tire use is to raise the front end with our fork swaps and let the back end sit lower by 1/2", yielding 27.0° steering angle roughly...

That change in KDX suspension balance altitude to 27.0° rake stance and 80/100-21 front tire with 21.5mm offset triple clamps yields EXACTLY stock 4.30" trail spec....
Changing KDX suspension balance altitude to 27.0° rake stance and 80/100-21 front tire with 22.0mm offset triple clamps yields just a hair under stock trail spec at 4.27" trail...

*NOTE - These triple clamp offsets vs rake/trail calculations DO NOT translate to KYB 46mm or KYB 48mm forks, or even the almost identical Honda CRF450X version forks, as the fork lug offsets may be different by as much as 2mm on these... I think the Honda forks if they have tighter lugs which they appear to have in photos, will be the better choice, or perhaps the RMZ versions although they don't have an offroad version to my knowledge, but even the CRF450RX is almost a motocross bike (it's a GNCC enduro racer setup) moreso than the predecessor the 2017-ish and earlyer CRF450X, so they will definitely need revalving. The KX450X was the most plush out of these, and many pairs readily available through ApplegateMX, + they have green anodized top caps!!!



22mm and 21.5mm offsets are available in aftermarket clamps,and 22mm in Honda CRF450/250 Showa clamps 2020's IF they have the same clamping diameters as the KX, or just use the near identical forks in Honda, they have black top caps vs the KX's green, luckily not Honda red!!!! I'm assuming from photos that the Honda lugs are still set back just a hair closer to fork tube centerline, as the angle of the lugs is steeper without a doubt.
So perhaps these CRF450/250 forks are the modern holy grail? I haven't looked into the RM-Z 450/250 versions, but I believe they are both 49mm Twin Chamber Showas also, the 450 is at least.
I will be looking into OEM Honda triple clamps now, however. Clamping diameters are the critical part since I already have these KX450X woods forks. They make a similar CRF450RX 49mm Showa Twin Chamber woods fork also, but this guy ApplegateMX on eBay has like 16 pairs of the 2023-ish KX450 forks from a race team last year's model buyout/part-out, with at least half being the woods version KX450X...


Also, I found a different set of KX450X forks, and asked this seller to measure the height for me, center of axle to top of gold outer upper tubes / bottom of the top caps, 37" is the measurement they returned me! (I just measured my new '24 KX450X forks at just a hair over 37", 37-1/16" max). My '97-'04 KX500 forks are 37-1/8", and my '98 RM125 forks are 36-7/8", so these are no deal breaker at all... taller than stock KDX by around 7/8", so right in the range of 3/4" - 1" taller than stock KDX as always with any good fork.

The 2024+ KX450X shock length is what I'm really waiting to hear back on now... "32mm shorter than 2019-2023 models" according to the DIrt Bike Test article on the 2024 KX250X (or was it KX450X?), and Teknik Motorsports lists 2023 at 475mm... the '24+ KX450X and KX250X shocks might be very well worth swapping to a '95-'06 KDX if they can maintain 118mm or more shaft travel after being internally lowered down to 438mm or 440mm + KLX suspension links and bolts to lower the rear closer to stock!

[Chuck78]

I've just emailed AllBalls about their lack of a 28x47x15 bearing, and also mentioned the 2019+ KX250/KX450 and nearly all '98+ YZ250 2-stroke stems perfectly fitting all water cooled '89+ KDX200/220/250 and KLX250/300/650 and '89+ KX500 models... *IF* one were to run a 28x47x15 bearing which is only available off Amazon/AliExpress or this New Zealand bearings website I found, says 5-10 days lead time to ship:

https://www.nzminiaturebearings.co.nz/p ... 84712.html

[kdxdazz]

All balls bearings are just cheap Chinese bearings anyway, I bought 3 lower shock bearings for the kdx from AliExpress but they are not full bearings like OEM, same as all balls, they are not full bearings

[Chuck78]

All balls bearings are just cheap Chinese bearings anyway, I bought 3 lower shock bearings for the kdx from AliExpress but they are not full bearings like OEM, same as all balls, they are not full bearings

Yes, I realize All Balls are definitely not premium bearings, although PivotWorks, another company under the same conglomerate ownership umbrella, offers the same products as All Balls, as well as their "premium" versions which are a bit of an upgrade in quality, but still no Koyo etc Japanese bearings.

Oh by the way, the 30x47x12 & 30x55x17 bearings and seals which I ordered from Pyramid Parts were in fact Japanese bearings, but they were NTN brand, not Koyo as I'd remembered incorrectly and stated above.

It seems that in bearings these days, it is very difficult to discern what is a fake/copy and what is genuine, as so many USA/European/Japanese companies have began moving some of their production to China, and we get genuine products of likely the same quality but cheaper labor from them out of China, as well as fakes that are selling for half price and say "Made In Japan" laser etched into them with the same logos and similar packaging... It's a real struggle in any field, industry, hobby - to get genuine quality parts these days. Owning older cars/trucks is a tough one as the repairs are only as good as the quality of the parts, and if the parts are all cheap, we have exploding fan bearings like on my wife's Toyota 3VZ-E V6 '89 pickup which took out the front main seal due to debris and damaged the timing belt!!! Frustrating... I should have thrown that in the trash bin when I did the timing belt and sought out a Japanese version, but they are scarce...

Right now, I'm digging through seal sizes to find a seal to match up to the 30x47x12 or 28x47x15 bearings. I may just order the All Balls upper bearing kit to see what part number seal they use. I need to pull my KDX forks and see how/where the upper seal rides. The one from Pyramid Parts is a larger O.D. and seems to be intended to sit above the frame, but if I'm using a 12mm tall bearing where a 15mm tall bearing formerly resided, I may switch to a different style of seal or else double seal it and have a 47mm seal mated to the press-fit bearing area of the frame above the 12mm tall bearing, and then stack a regular seal on top of that, as it appears the KDX seal sits at the top above the frame with a lip extending down into the bearing. It's been an embarassingly long time, a few years, since I've greased either of my KDX's steering stem bearings... the memory is a bit foggy as to the exact fitment now!

[Chopperpilot]

I've just emailed AllBalls about their lack of a 28x47x15 bearing, and also mentioned the 2019+ KX250/KX450 and nearly all '98+ YZ250 2-stroke stems perfectly fitting all water cooled '89+ KDX200/220/250 and KLX250/300/650 and '89+ KX500 models... *IF* one were to run a 28x47x15 bearing which is only available off Amazon/AliExpress or this New Zealand bearings website I found, says 5-10 days lead time to ship:

https://www.nzminiaturebearings.co.nz/p ... 84712.html

I'm curious about the 15mm dimension. As I recall, the bearing I got was listed as 28 x 47 x 12mm. Now measuring the bearing with the race on it showed up as 14.5-15mm (if I recall correctly). Regardless the thickness is just right. I'm going to measure the KDX bearing set when I get it in and see what it comes out as (with race) vs what it's listed as.