H Series with Kayaba SSS fork assembly from a Yamaha

[soup-n-sandwich]

Hi guys,
I'm in a bind right now trying to get some information about an H series KDX (before this used KDX is sold out from under me) and what it would take to swap out the conventional stock fork with front end from a YZ 250.
1) Would this work and if so what is involved?
2) Is the SSS KYB fork the same length as the stock fork or would the SSS have to be shortened?
3) Is the SSS fork just as usable in terms of installation modification as any of the KX fork conversions or are they a completely different animal?
4) I've been hearing a lot about the guy that was doing the fork swap conversion is retiring. Is this still the case and is there anyone else that has the skills and machines to do the fork swap?

Thanks guys
C

[doakley]

it's actually not that hard but you will need the forks and a matching triple clamp set. You press out the Yamaha stem from the lower triple clamp and press in your existing KDX stem. You'll probably have to shim the top triple clamp stem to make it fit correctly.
I used KYB forks from a KX250 and did not have to shorten the forks. I did have to raise the fork tubes in the triple clamps to get the geometry right. You may need bar risers to get the space to raise the forks.

[SS109]

Yup, what Doakley said.

The toughest part is that you might have to have the KDX stem knurled to fit the YZ lower triple clamp. Ron Black does that but, if he's not taking any more work, any competent machine shop should be able to do it rather cheaply. Also, Ron's top clamp spacer, while not mandatory, is a really nice piece to complete the swap.

Also, to do the swap you'll probably want the axle, wheel, and brake caliper to make it all bolt up without a fuss.

[soup-n-sandwich]

Yup, what Doakley said.

The toughest part is that you might have to have the KDX stem knurled to fit the YZ lower triple clamp. Ron Black does that but, if he's not taking any more work, any competent machine shop should be able to do it rather cheaply. Also, Ron's top clamp spacer, while not mandatory, is a really nice piece to complete the swap.

Also, to do the swap you'll probably want the axle, wheel, and brake caliper to make it all bolt up without a fuss.

Thanks very much guys. There is a lot to it when it coes to making a KDX on the same page with a "modern" bike. Since I'm going to race this bike I want to make the bike everything it can be. I'm going back and forth between the KDX and a YZ250 with the necessary mods to become a good offroad bike rather than an MX bike. Since the KDX220 must be raced in the 250 class it's at a disadvantage so I was looking for a 200 rather than a 220 for this reason. I love the KDX but need to address it's weak points. The suspension being the first on that priority list. Having the Kayaba SSS fork would be a major step in the right direction.

Do you guys know if the shock off the YZ would fit the KDX or should I be starting up another topic for that question?
C

[doakley]

If it were me, and I've been there, I would send the shock to Jeff Fredette and discuss with him. He does his own revalving to the rear shock and it is excellent (IMO).

[KDXGarage]

Check to see where the KDX steering stop is going to contact the YZ lower triple clamp. For example, an aluminum frame KX250F (2006) has the stops on the clamp differently than the lower clamp for the steel frame.

I would just rebuild / revalve the stock shock.

[SS109]

The stock KDX is pretty decent and especially so if a competent suspension guy revalves it for you. That said, the YZ shock will NOT fit. The one series of shock that will fit, as I have one on my own bike, is the '01-'06 Suzuki RM125 Showa shock with some mods but this mod isn't for everyone. Here's a link to this shock swap: Full Showa USD fork/RM125 shock conversion

UPDATED: I have changed this post to eliminate any confusion on the Showa shock swap and have included a link to all the info on this swap. I also split off the recent discussion of this swap also to that same link and starts at the last post on Page 5.

[ebulic19]

Hi guys,
I'm in a bind right now trying to get some information about an H series KDX (before this used KDX is sold out from under me) and what it would take to swap out the conventional stock fork with front end from a YZ 250.
1) Would this work and if so what is involved?
2) Is the SSS KYB fork the same length as the stock fork or would the SSS have to be shortened?
3) Is the SSS fork just as usable in terms of installation modification as any of the KX fork conversions or are they a completely different animal?
4) I've been hearing a lot about the guy that was doing the fork swap conversion is retiring. Is this still the case and is there anyone else that has the skills and machines to do the fork swap?

Thanks guys
C

How did this end up for you? Did you have to get new steering stem bearings in the conversion?

[soup-n-sandwich]

Hello Ebulic19,
Well a few thing have changed. So I have a 48mm Kayaba SSS fork off of a Kawa KX450 instead of the Yamaha. The steering stem has been pressed out of the OEM KDX bottom clamp and refitted to the triple clamps of the KX450. I have new stem bearings also but haven't pressed them on yet. I'm working on the rebuild of the engine now and will send the fork and shock to get worked on as the fork for the KX450 is a tad too long compared to the KDX fork. I'm talking about the distance between the center of the axle and the top of the fork. Overall the KDX fork is actually longer but that doesn't really matter as it's not the critical measurement. The suspension needs a revalve too so it's all going to Factory Connection in NH. A while ago I posted lots of pictures showing the weights of every component I took off of the KDX as I broke everything down. Funny thing is that the KDX fork and clamps where 5 pounds heavier than the much larger 48mm units off of the KX450!

The progress has been slow but this is only because I'm working on the shop to make the rest of this project much easier. Adding a spray booth/welding area with a 3200CFM blower that will suck the paint off the walls. I'm almost done with this and then I can resume on the rest of the complete rebuild, but I'll keep everybody posted as progress is made.

[brademan76]

Lots of different triple options for using 48mm SSS/AOS forks on KDX without swapping over the stem. The key is the adapter bearing and triples with appropriate length stem. Lots of discussion here:
viewtopic.php?t=26420

[ebulic19]

Hello Ebulic19,
Well a few thing have changed. So I have a 48mm Kayaba SSS fork off of a Kawa KX450 instead of the Yamaha. The steering stem has been pressed out of the OEM KDX bottom clamp and refitted to the triple clamps of the KX450. I have new stem bearings also but haven't pressed them on yet. I'm working on the rebuild of the engine now and will send the fork and shock to get worked on as the fork for the KX450 is a tad too long compared to the KDX fork. I'm talking about the distance between the center of the axle and the top of the fork. Overall the KDX fork is actually longer but that doesn't really matter as it's not the critical measurement. The suspension needs a revalve too so it's all going to Factory Connection in NH. A while ago I posted lots of pictures showing the weights of every component I took off of the KDX as I broke everything down. Funny thing is that the KDX fork and clamps where 5 pounds heavier than the much larger 48mm units off of the KX450!

The progress has been slow but this is only because I'm working on the shop to make the rest of this project much easier. Adding a spray booth/welding area with a 3200CFM blower that will suck the paint off the walls. I'm almost done with this and then I can resume on the rest of the complete rebuild, but I'll keep everybody posted as progress is made.

Thanks for updating. I am eying up a set of KYB SSS off of a 2016 YZ250F, along with complete triples, front wheel w/axle, and the complete brake front brake system for $400. Does that sound like a fair price? I have not a clue what the part-out market is like.

The KDX fork is much longer top to bottom of lugs just based on how low they hang underneath the axle i'd presume, correct?

Enjoy the shop! Thanks again for reaching back. I am trying to do as much DD as possible before purchasing anything.