Hi All, just sharing my experience on an easy way to do the KX swap. Disclaimer: This involves parts originating from a certain Asian county, longevity has yet to be tested. I haven’t ridden the bike yet, other work is being done to it but I will update as I go along. I might be the first to try this, I don’t know if it’ll work for you. I’m not saying you should go this route, just posting my experience.
Anyway, here’s the setup. 2001 KDX200. 2000 KX250 front end. The problem is that the upper bearing previously had prevented a direct swap. The bottom bearings on the steering stem are identical, 30x55x17. The upper bearings are: KDX: 25x47x15 KX250: 28x52x16. An adapter bearing, 28x47x15 previously didn’t exist, but it does now. If you google it, you’ll find it. A 28x47x12 is also available and should work. I purchased said bearing to test doing the swap this way.
Happy to report that it does work and fits near perfectly, making the KX front end a direct bolt on. The taper on the bearing is identical as evidenced by grease witness marks. The only thing I used from the KDX is the dust cap. Everything else is KX. It fits near perfect. No play, slop, nothing. Steering is smooth, no weird binding. No spacers or shims needed. Not sure if anyone else has gone down this route. But if it works in the long run it’s much better than swapping the stems. As a bonus, I can switch back to the stock forks in minutes. I’ll continue to update as I ride the bike and eventually revalve the forks. Let me know what questions you have.
That’s the interesting thing. The stem on my KX parts bike was shorter than the KDX by about 1/2”. I’m assuming it’s stock, but you all might tell me otherwise. The lower nut is tightened down on the lower bearing itself.
Lower nut
dust cap
Upper bearing
The way I have it assembled is no different from the stock KX.
So the 2019 and up KX stems are about 7 mm longer than a KDX stem approximately. Does anyone have any documentation / specs on the length of KX stems starting in 1999 through 2018 on both two-stroke and four-stroke models? I say 1999 as that was the first year where the inverted forks had absolutely no tube underhang below the axle lug. The 1996 - 1998 forks are a great swap still but might as well go for the gold when swap shopping.
1/2" shirter stem? What year was that?
Later generations Honda CR250R & all CRF250 & CRF450 steering stems are nearly a perfect direct swap using a Japanese NTN bearing or All Balls bearing 30x47x12, plus a 3 mm spacer below the bearing race or above the bearing inner race. I would never even bother doing a KDX stem swap using the heavy steel KDX steering stems, and the aluminum KDX 250 steering stems probably are not the correct press fit diameter for the modern forks.
It's unfortunate that Kawasaki used a 47 mm outside diameter upper race, because if they used a 48 mm, then we would have 25 mm, 26 mm, 28 mm, and 30 mm industry standard size bearings available to do all sorts of fork swaps. Machining out the frame would be quite an endeavor since the frame is welded together, however it could be done with some sort of fly cutter or boring bar setup adjusted out in small increments after getting up very thorough frame jig setup made to hold the weight of the KDX frame up on the bed of the mill.
I have often wondered if the angles of the bearing races would be similar between a 47 mm and a 48 mm bearing, as one could just do some swapping of races to get a full 15mm height bearing in there in a name brand, however I would almost guarantee that the angles of the bearings are different by a slight degree or two.
The best solution as best as I can tell would be to use a 30 mm ID bearing which is the largest you can get in a 47mm o.d., and turn a simple top hat adapter in a lathe to sleeve the inside race of a 30x47x12 bearing down to 28mm, with a flange on the top so that it does not drop through the bearing. A slight interference fit on the bearing side but 28mm-ish inside diameter on the stem side to mimic the exact dimension of the 28mm stem bearings. A tight slip fit but not an interference fit.
Swapping a Honda CRF steering stem into a KX or RM triple clamp what also be a pretty obvious solution, as long as the press fit sizes were identical. If you are talking 2006 and up KX250F, they are going to be both Showa forks so the triple clamps are probably identical.
I may likely try to score a cheap 1998-ish CR250R lower triple clamp just for the steering stem, to see if it is going to be a better fit for a modified (shaved lower bearing seat) '98 RM125/250 triple clamp, otherwise the Suzuki V-Strom DL1000 aluminum steering stem I have here will work out perfectly except it's going to extend above the upper triple more than desired.
