KDXRIDER.NET

After reading all the post regarding the fork conversions for the KDX I am curious. I have a complete front end for a 2001 YZ426F, has anyone ever tried this conversion?

Not that I have seen, but pretty much anything is possible with some creativity.

I've done over half-dozen yz to kdx fork conversions, including the 94 KDX I currently own. The yz fork installation is the same for both the E and H KDX models. In my opinion the yz's are one of the better sources for kdx conversions based on:
1. The 1998 thru 2003 46mm forks (yz125's, yz250's, and yz4**'s) use a top-out bumper that can be removed and replaced with a washer, so the forks can be shortened and still use the stock springs with normal preload. yz125's =41 yz250's=43 yz426=46kg/mm
2. The later yz's have the handlebars situated further forward in the triples which improves a kdx's handling noticeably. 2001 on up is furthest forward.
3. The yz triples are just the right thickness for the stem nut to seat properly with just a thread or two showing. No spacer required. You do need to install some shim stock around the upper stem slightly larger hole (I use aluminum pie plate material).
4. Most, but not all, stems require knurling, just like for the kx triples, but some fit without it - strange but true even for the same year triples.
5. The H model kdx nissan brake caliper is a bolt-up with the yz caliper bracket. The E model brake caliper will not work with the YZ forks.
The only minor drawback is you need to slightly increase the steering stop width.
IMO, these are better forks than the KX kyb's, they don't use bladders and are very easy to revalve for off-road by simply modifying the compression stack.
The forks on this 94 kdx have been shortened 3/4" and revalved by modifying the compression stack into two-stage damping. They work extremely well in all kinds of terrain, very absorbent of trail trash, but can still handle huge hits very well. The bike went from relatively poor handling to great with this modification - and that comparison is based on the 94 forks having heavier springs and gold valves - they still didn't "cut the mustard" for me... the bar position change really helps with the bike's higher speed turning and handling also - as your body position is more centered (neutral) so you no longer have to force yourself over the bars to get the front end to bite at speed.

Welcome back, stranger!

Great post. Thanks for sharing your experience.

You're welcome! Yep, I still lurk around here - great site for a great bike!

Kawagumby, That is good news to hear regarding the YZ fork installation. I will also be making this attempt on an 95 H model. I assume you also had to use the matching YZ front wheel? I have the complete set of forks including triple clamps and front axle, but still need to find a front wheel. Since you mention the knurling and shimming you must be using the KDX stem?

Yes, you will need a yamaha front wheel, axle and spacers. The KDX stem is used, from either an E or H model (they're the same). If you notice from the picture, what I did to mount the yamaha brake line clamp involves a 3/4 x 3/4" aluminum angle pop riveted to the fork guard. I've used that on several bikes with no issues.
Also, most of the KDX's I've used these forks on did not need to have the forks shortened, as you can slide them up in the triples to get the right geometry if you use fatbar adapters or bar risers to get the clearance needed. For my weight (150 lbs W/O clothes) the 125 springs are right on, for heavier riders 170 up, the stiffer springs would be better.

1998 + stems are about 0.007 " thicker in my experience.

Interesting...that might partially explain why I've encountered situations where knurling a stem both was and wasn't required for same-year yz triples.

Is the KDX stem required in order to use the stock bearings?

yes, bearings and length...

Sorry to keep asking a bunch of questions. I read that the YZ caliper bracket is needed but what brake rotor do you use for this conversion. I am sure it is the YZ because of the mounting bolts on the wheel, but what year for correct diameter?

No problem.
You just need to match the caliper bracket to the year of the wheel/rotor. Starting 1999 the stock rotor is a "floating" type and is slightly larger than earlier models so the bracket would need to be from that year or later...

Thank you for the info. I need to start collecting a few more parts and then make the switch.

I have started this conversion and noticed that the steering stop allows the fork to turn to far and back into the radiator. How did you solve this problem?

I weld a wider piece directly to the existing stop. If you don't have a welder, you could probably bold one on.

Thanks for the reply. I think I will try bolting one on that lengthen's it on both ends.

I have seen kawagumby mention in multiple posts that you can remove the top out bumper and replace with a washer in the yz forks to shorten them.

My question to you guys is do you need to do anything else to the fork Internally?

Do you need to add a spacer to the damper rod somewhere to compensate for the new free space?

Two separate times in about 2 years, I have spent about $ xxxx.00 on my suspension, both ends. My KDX is riding and running great. REALLY great. But man, what is seen can't be unseen, and I can't get this YZ426F conversion out of my mind. I have started cruising craigslist for donor bikes.

I know that I have issues. My wife reminds me and the E (G) has alluded to as much, to my wife and me. I just hope that I do not locate a YZ 426F front end. Maybe I can find a KDX220 and start all over and have 2 race ready KDX's-

I am sure she will be thrilled. If you get those forks, she and I can take turns whacking you over the head with them.