KDX to KX front end conversion - Complete!

[TVRider]

I finished putting a KX125 front end on my '03 200 last night. I can't say enough good things about Skipro3. :worship: He walked me through serveral steps by email. It's always easier to ride a trail when someone else clears the way a little. I know he wasn't the first to do this but he was a big help to me. :thumb:

All that said, I can't beleive how easy this was. If your considering it, go for it. Here is a breakdown on the process and parts I used:

1. 2000 KX125 forks and front wheel assembly, '99 KX250 triple clamps, '03 KDX200

2. Remove KDX forks and t-clamps. Press KDX stem out of t-clamps and into lower KX t-clamp along with the lower bearing. (other have had to knurl and locktite, but these years were a press fit).

3. Mount KX t-clamps on KDX frame. Use the KX steering stem nut or appropriate size washers to shim under the top t-clamp as the KDX stem is a little too long.

4. The top t-clamp is a little loose on the KDX stem. Go to the local hobby store and buy some .025 brass shim stock. Use this to form a shim around the stem in the top t-clamp.

5. Finish bolting everything together and go ride. :yeehaw:

I've only done the first 1/2 of step 5. I'll give you a ride report soon.

Tom

 

[CaptainObvious]

That does sound simple. Were you using the stock springs in the KDX forks? Did you have enough experience with the KDX forks to make a true comparison.

I would expect that your ride report will go something like..."the forks feel just like they were off a KX125!" I look forward to your ride report.

 

[TVRider]

I was using the longer (530mm) springs out of an '01 XR400. I had about 100 miles on the newer springs. The KX forks had the bladders removed and the valving softened somewhat already. I used the stock springs out of a 99 KX250 in the KX forks (they came with the forks). When I got the forks they had .43's in them and the '99 stockers were lighter and a progressive spring according to Jeremy at MXTech. He thought they might work pretty well for the woods so I swapped them.

As for the experiance to give a true comparison, I am, by my own admission, not a real fast rider. I did the conversion because the KX front end was cheap, it sounded fairly easy, it was a potential big improvement and I love to tinker. :)

Tom

 

[canyncarvr]

re: the kdx stem is a little long.

How does it 'get' that way? The kx clamps are thinner than the kdx clamps? Does the kdx stem have less of a bite in the bottom clamp, then?

Where does the extra length come from?

Seems the kx clamps would be thicker..and thus the stem too short if anything. That not being the case....??

Did you use your kdx brake cylinder to a kx caliper? What was the lash up there?

No odo I'm sure. Hey! I like the oem odo!

I do get irritated at the kdx fork underhang, though.......

Look forward to your opinion.

How were the kx forks setup? Revalved? Stock? Spring rate?

 

[Kawadougie]

The difference in length in the steering stems is simple. The steering heads are of a slightly different length. Complicating the installation is the fact that the KDX upper bearing is smaller in diameter than the KX although the lower one is identical. The KX steering stem is made of steel and is much smaller at the top. The KX stem is aluminum and has a larger diameter for strength. There isn't enough material to turn it down safely so you have to use the KDX steering head. I used YZ-125 forks and front wheel for my upgrade although I used a KX-250 lower clamp so I didn't have to redrill my fender or modify my WER steering damper if I decide to put it back on. I think the KX250 lower clamp fits better since I didn't have to mess with any shims or knurling. This is a fairly simple swap and there is absolutely no comparison between the stock forks and these. It now sails through the whoops and I can slam through things that I had to slow down for before. I used to run XR400 springs in the stock forks. My USD forks have heavier springs than Skipro's because his is much softer than mine. We've gone riding together a few times.

 

[JasonWho]

---

 

[TVRider]

I did some measuring after the fact (a little tough after everything is assembled) and the KX lower triple is about 4-5 mm thinner than the KDX lower triple. The washers I used for shims amounted to about 7mm. I didn't have a KX stem or steering head nut so that's what I ended up with. The machine shop I used was FTZ racing here in Cape. John has a nationwide rep as one of the best engine builders for mini sprints. They told me it was a press fit and they would be comfortable riding on that stem, good enough for me. They did express some concern over the knurl and loctite method but since mine was a press fit that wasn't an issue.

The KDX brake cylinder, cable, caliper and all dropped right onto the KX forks and front brake disk, no modification neccessary.

As far as how the KX forks are set up:

Stock 99 KX250 springs .42-.43 (as I mentioned below Jeremy Wilkey said that year KX250 had progressive springs). The forks had been softened by removing the bladders and revalved by C-Cycle (a shop the former owner used). NEMX305 (the seller of the KX front end) recommended futher softening for really tight wood riding. Jeremy recommended riding for a while to see how I like it. I went out in the street and hit the curb coming back into the driveway hard and it soaked that little bump up like it was nothing. That's the extent of my riding so far. I hope to go riding a little with my son on Saturday. I'll keep you posted.

Tom

 

[dead]

Thanks for the info! :thumb:

 

[skipro3]

Glad to hear all is going well TVRider. Too bad you're not closer to California to take a ride with Kawadougie and I. He's an animal on the trails and would show you just what that front end is capable of. My knurled lower t-clamp is holding up great, even after several crashes. (Another story, but not the fault of the front suspension). Somewhere on this forum I posted photos of my odometer from a mountian bike. It is trick and works great. It even gives me the air temperature!! I will send photos of the odo and the forks on my bike if anyone is interested and can't find in a search.

 

[Timr]

I'm curious about one thing.  On many previous front end conversions, people have mentioned that they have swaped out the KDX rear shock for a KX one that's a tad longer.  This was done to ballance out the difference in the fork length, and make the entire bike sit up a little higher.

Doe you guys have problems retaining the stock shock with the stock dog bones?  Is the front end higher than the rear?  Do you have the forks all the way up in the clamps?

 

[TVRider]

Tim,

I haven't played around with the forks in the clamps yet. When I rode it briefly last night it was certainly taller at the saddle so I would say the KX forks added some height in front. I'm veritcally challenged (5'8", 30" inseam) so I have Devol suspension links installed to lower the KDX a little. The nice thing about the Devol's is you can go back to standard or even raise the rear a little. In talking to Jeff Fredette for an opinion about this mod, he thought it would be a big improvement. I asked about the rear shock length and he didn't think it's an issue. I guess if the front end is elevated it will be easier to loft the front wheel (or loop out on a big hill :eek: ). I'll probably end up moving the forks up in the clamps.

Tom

 

[skipro3]

The KX rear shock won't bolt up to the KDX in stock form. It is too long and will hit the swing arm. I tried. There may be some rods to modify, but why bother? The shocks are basicly the same anyway. Play with the preload (sag) and go with that. The KDX rear suspension is as good as it gets in stock form for the average weight rider and has compression / rebound adjustments. I have found that the settings are critical to good performance. For me, at 175lbs and KX125 front suspension, it is 12 clicks on the top from full out and 3 clicks on the bottom from full out. I recommend you make adjustments from full out instead of full in. An agressive hand trying to get one more click in will damage the shock. It is obvious when you have turned full out, but not full in. Just my opinion.

 

[Kawadougie]

My forks are slid up in the clamps about 1/2" right now and the bike feels pretty level. You could move them up 1" max. The other thing to mention is that if you go "98 or newer with the Kayaba forks you can use your stock brake caliper. That's the year they apparently changed the brackets.

 

[TVRider]

I went out for my first ride on the new front end today, just me and junior on his TTR so nothing radical.

The front end felt very plush, I mentioned they had already been revalved (I'm waiting on an email detailing the setup) and I started 12 clicks in on both rebound and compression. I also tried 10 and 8 clicks on both. 12 felt pretty good, 10 felt better (it seemed to soak up the small stuff) but 8 clicks seemed a little harsher. I'm new at the suspendsion adjustment but that seemed odd to me. It could be it was my imagination. As I rode around with my son, I tried to hit any sharp edged bump I could find and just generally hit stuff at a higher speed than normal. Either my riding has really improved or these forks are awesome!! :yeehaw: Before I always felt like the back end was doing it's job but the front end just couldn't keep up. Now it's definitely the opposite. I will need to do some adjustment on the rear because it felt pretty harsh by comparison. I did a few small jumps today (not exactly my forte') and tried to land hard on the front to see how it would react ( I didn't have to try too hard as this is my normal style :silly: ) and I just couldn't upset this front end, it floated through everything I wanted to throw at it in a casual ride. Please keep in mind I'm NOT a fast rider, I want a suspension that keeps my out of trouble when my right wrist get the best of me and this is a big step in that direction. Hope this helps. Ask questions and I will try to answer.

Tom

 

[skipro3]

You expressed exactly how I am experiancing the KX suspension on my KDX. Play with the rear settings and if possible, have someone follow you to let you know how it looks. Mine was set with too much rebound and was spanking me in the butt on every sharp lipped edge I was climbing at speed. Kawadougie spotted for me and we got it dialed in. Now the back is balanced with the front and they work well together. Also play with air pressure in the tires. I was running 12 to 15 lbs and found this too harsh and wouldn't allow my tire to hook up well. Now at 4-8 lbs air, it is much much better traction. This mod has helped me get back into riding again with my old (out of shape) body. Other than more felt vibration in the hands, it is all positive and very easy mod to accomplish.

 

[TVRider]

The t-clamps I used are out of a 99 KX250 and the top clamp had handle bar isolation bushings ala the KDX so the felt vibration is about the same. I'll give your other suggestions a try. :thumb:

Tom

 

[tedkxkdx]

On my 96 kx on 96 kdx, I was running the extra washers that shim the steering head nut on the top of the triple clamp. I wanted the front end to turn sharper so instead of moving the forks in the clamps I put the three washers under the clamp and thus did have to move the forks to re-level them in the top clamps. The result was very noticeable in my berm turns.
I am glad to see that many more people are waking up to the fork conversion, cuz I feel that it makes it a completely different machine.

 

[skipro3]

Burms are now explosive! I love it! My only limitation in berms is my courage. Since conversion, I have not overshot a berm yet. lean it over and hold the throttle pinned and it will track a berm like it is on rails. Did I say I love my conversion? This thing rocks!