‘00 KX250 Swap Items

[Chuck78]

I'm curious as to the KX stem length from that era of fork as well, as the 1999 and newer are much preferred due to the better lower lug design that does not have any underhang at all.

The steering stems got 3mm longer I believe I'd read starting in 2019, and I have a 2020 KX250F triple clamp for these '24 KX450X race team take-off forks I bought, and it's a very workable stem although about 7 mm longer than preferred, but that's fine - as adding a spacer up top between the bearing / seal and the nut and running the longer stem will just move the upper triple up higher making it so that running the forks flush with the top of the upper triple clamp is effectively dropping them 7 mm in ride height down without getting any closer to the handlebars, since all of these forks are at least one inch longer than the stock KDX, every bit helps.

I believe the 1999 - 2000's/2010's steering stem is closer to the KDX length, so less of a spacer would be needed, and should be completely workable.

I'm always opposed to swapping the heavy steel old school KDX steering stem into a pair of triple clamps for a modern fork, as you are just downgrading the triple clamp with a lot of unnecessary weight and added complications with having to press it out, neural the stem to make it increase its diameter just to fit the newer triple clamp, as well as machining a bushing to fit the top triple to the KDX steering stem.

The only downfall to this is that the 28 mm upper bearing i.d. of 28mm doesn't leave us with any industry standard sizes available, and unfortunately the only bearings available in this 28x47x15 & 28x47x12 size are of random Chinese origin.
Most people run Chinese bearings when they buy them from All Balls anyways, but at least those are somewhat known quality albeit not as good as the Japanese or European or Mexico/American made bearings.

The Honda CRF250/450 & later CR250R steering stems are the perfect bearing distance spacing and use a 30mm upper bearing,, which can be had in reputable name brand bearings as pyramid Parts in the UK sources Japanese made NTN bearings in this size. If I run this KX steering stem, I will be using an NTN 30x47x12 bearing and machining a reducer bushing with a flange on the top to keep it from dropping through the bearing, 1 mm wall thickness, to sleeve the 30mm bearing down to 28mm. I may likely though just pick up another Honda triple clamp (whatever I can find for cheapest on eBay) and use the steering stem in the KX triples, as they are both made by Showa and should be the same press fit diameter.

[Bz1hx]

Your posts on the other thread is what prompted me to do some digging on this. Thank you for all the info and potentially saving me from going the stem press route! I went ahead and ordered the bearing so we’ll see what happens. It’s Chinese no doubt, but the bottom bearing takes most of the load and it’s not as if they’re spinning all the time like a wheel bearing.

I’ll compare the stem lengths when I get home and post it here. For reference, I have a 2001 KDX200 and the complete front end from a 2000 KX250. If it works I’ll be thrilled. Hopefully shipping doesn’t take forever (it probably will)…

[Chuck78]

I haven't measured the stock stem but I figured around 190 mm bottom of lower bearing seal area to top of upper bearing area on the stem is about the perfect height. The 2019 and newer are around 197 mm for that same dimension on the steering stem. I'm curious to see what the KX stems 2018 and earlier measure, in light of these newly available bearing sizes. Thanks for your help in gathering that information!

[Bz1hx]

Alright. I’ll do my best to explain this. First off, the measurements aren’t 100% accurate because the stems are still pressed in, but fairly close. Both stems are measured on their total length. KX250: ~266mm. KDX200: ~292mm.

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However. When both stems and triple clamps are stood on the bench, the inner race of both bottom bearings are parallel. So, when stood on end, the taper for the upper bearings line up almost exactly and the threads for the bearing retainer nut line up. This just leaves the upper threads that don’t align as the KX stem is about a 1/2” shorter.

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If those measurements aren’t helpful, let me know and I can re-measure. So, will it work? Idk. I’ll mock it up on the KDX this weekend when I get the front end off.

[Chuck78]

The full length of the stem doesn't matter because it's functional length is completely dictated by the thickness of the lower triple as well as the thickness of the upper triple and to a lesser extent the nut used on the steering stem. Bottom of the lower bearing / seal press fit area up to the top of the upper bearing area is the critical dimension. 190mm-ish ir around 7.5" is the good height. Differing steering stem nuts will also affect that, but a Honda steering stem from a late model CR250R or basically all CRF250/450 models that I have seen measurements on, is nearly perfect when used in conjunction with the correct bearing sizes and the nuts intended for those stems. YZ250 2-stroke steering stems from the 2000s and on are nearly perfect as well at around 192mm iirc, & newer model YZ250F and most YZ450F steering stems are also acceptable at just below 190mm iirc. I'm going to take a guess that you will find the Yamaha WR250 and 400/426/450 stems will also be comparable to the YZ. YZ125 2-stroke & some YZ250F (early models) 4-stroke steering stems are too short by a fair bit. So are Suzuki RM & DRZ stems, but a VSTROM DL1000 not ABS aluminum stem is nearly the perfect height although the upper triple portion is much taller, but the bearing height is perfect. A spacer would be needed or else cut the top of the stem off and tap the inside for a big threaded bolt you can find something lightweight and suitable in the aftermarket. Or just thread the top of the stem lower and cut off the top portion.

[Chopperpilot]

I found the 2 stroke YZ 250's stem to work great with that 28mm adapter bearing. Also, if I read your first post correctly, you're a big guy, so you may not need to go crazy re-valving the forks (and this is coming from someone who thinks everything should be re-valved). I'd probably try to soften the mid valve some and do the float as recommended, but your weight would make the MX suspension more 'trail friendly' by itself.

[KDXGarage]

Maybe not. I rode my 2005 KX250 with stock damping and the compression adjusters set to full soft. This was with slightly too soft springs for my weight. It beat my wrists to death.

[Bz1hx]

Well, I got the front end off the KDX last night. The bearing races were mint, very happy about that. With the KX stem on the bike and visually looking at how things line up, this is looking very promising. More to come once that bearing shows up.

I found the 2 stroke YZ 250's stem to work great with that 28mm adapter bearing. Also, if I read your first post correctly, you're a big guy, so you may not need to go crazy re-valving the forks (and this is coming from someone who thinks everything should be re-valved). I'd probably try to soften the mid valve some and do the float as recommended, but your weight would make the MX suspension more 'trail friendly' by itself.

Yep, you read correctly. My first move will be to crack open the forks and just do a rebuild. I’ll play with the valving as needed from there.

[Bz1hx]

It’s good news!! With the 28x47x15 bearing the KX front end becomes a direct bolt-on. I re-used the KX lower bearing as it was in good shape. There’s no slop, play, or loose-ness either up/down or side/side. Steering is smooth with no binding. No washers or spacers needed. I used the KDX dust seal, everything else is KX. If anything, the top nut doesn’t thread quite all the way on, but nothing a little blue loc tite can’t fix. Obviously, the bearing is the product of a certain Asian country, so time will tell if it holds up. Seemed to be of decent quality though. It’s not completely bolted together as the forks need to be rebuilt. But here’s the proof.

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[Chuck78]

Great to hear!
In case the generic bearings don't seem to hold up well, I might at some point start making 30mm bearing adapters to the 28mm stem size to use Japanese NTN bearings on the upper position if there's enough interest, but that's a long way off since I've discovered Honda steering stems all use a 30mm bearing i dm upper and lower. Honda forks of interest are almost all closed chamber Showas and some closed chamber KYB's, whereas the '99-'05 KX / KX###F forks and Yamaha '04 YZ & '04-'05 WR are KYB open chamber forks of interest that both use a 28mm upper bearing. Open Chamber forks are simpler to rebuild, have less parts, slightly lower weight depending on some factors, and are generally easier to valve nice & plush for woods riding, do those forks are of great interest to our needs still and use the 28mm upper steering stem bearing... All the KX years seem to use the 28mm upper stem o.d. (bearing i.d.) it seems.

Looking at bearing size charts, Kawasaki could have made things easier on us if only they'd used a 48mm o.d. on the upper bearing instead of a 47mm!!! 25mm, 26mm, 28mm, & 30mm i.d. bearings are available in industry standard sizes for 48mm o.d.!!! We're 1mm off! Opening up the frame i.d. 1mm by removing 0.50mm material would be a nightmare to get jigged upbto bore accurately, so no thanks...

I'd personally mill a bit off the top raised pad on the upper triple to get full thread engagement on the top steering stem nut, but that's just a minor detail.

[Bz1hx]

I suspect I’ll get more engagement on the top nut after one change. The ID of the dust cap causes the bottom nut to rest on top of it when tightened down. Thickness of the dust cap is about 1mm. I should be able to open the ID up and then the bottom nut will tighten directly onto the bearing (please correct me if this is a bad idea). That will then lower the whole assembly and top triple and I should be able to get full engagement of the threads on the top nut.

[Chuck78]

I suspect I’ll get more engagement on the top nut after one change. The ID of the dust cap causes the bottom nut to rest on top of it when tightened down. Thickness of the dust cap is about 1mm. I should be able to open the ID up and then the bottom nut will tighten directly onto the bearing (please correct me if this is a bad idea). That will then lower the whole assembly and top triple and I should be able to get full engagement of the threads on the top nut.

Sounds good, but make sure you keep it perfectly concentric and make sure that the seal will still have pressure on it keeping it forced downward into the bearing and against the frame, so perhaps this is not a good idea considering that last bit. I'm not sure what the nut is shaped like if it has an integrated collar/sleeve below it like the KDX stem beearing nut does.

[Bz1hx]

The lower nut on the KX is just a splined nut. No collar. I’m sure I can trim the dust shield without causing an issue. I’ll work on it and report back.