YZ/WR 48mm Fork Swap on 1989

[jaunt]

Just wanted to share where I'm at with this, maybe it could help someone else.

All the parts came with the bike, not sure where the triple clamps were sourced from but they had a KDX stem installed already. I'm just seeing how things fit up and it all seems pretty good. I'll be pulling them back off and doing the stem bearings and fork seals. I also plan on using a CR brake hose to eliminate the wacky front brake hose routing.

[SS109]

Sweet! Keep us posted!

[Chuck78]

48mm Closed Chamber KYB "S.S.S." forks came on:
WR250F 2015+
WR450F 2012+
YZ125, 250, 250F, & 450F 2006+ (RaceTech says 2005+)
YZ125X / YZ250X all years ('20+/'16+?)
Italian-built Husqvarna ('06-'14-ish, pre-rebadged KTM era)

The top caps on yours aren't fully recessed with bronze outer ring, so I believe these are open chamber forks, which are much easier to rebuild and easier to get valve plush then closed chamber / twin chamber SSS type forks. Since they are 48, I would think they might be off of 2006-2014 models that aren't included in the SSS list above.


Here's some good info about the top caps, photos to conpare yours:

https://www.thumpertalk.com/forums/topi ... -sss-fork/

Look up WR250F / WR250R forks '06-'14 & WR450F/R '06-'11, & that's my best approximation of what you have. I'm not sure if you would be able to tell what spring rate you have but the 450 is likely to have a stiffer spring.

www.RaceTech.com/ProductSearch is very useful in checking out types/sizes of forks, stock spring rates. Unfortunately it says "please call" in the information category for WR spring rates instead of an actual rate, when I browsed a couple years of 250R's/250F's. I use this all the time when looking at fork swap criteria / info.

[Chuck78]

Check the 04 or 05 or other early 2000s models as well, in YZ & YZ###F, see if any of those came with 48 mm forks. If they did, then it's not quite as straightforward or pointing to the WR as I originally thought.

*Update - '03 YZ250F shows 46mm forks, '04 shows 48mm KYB Open Chamber forks, '05+ shows 48mm KYB Closed Chamber (SSS). So if they're not a 2004 or maybe 2005 (according to other websites '06+ was SSS, RT says 05+), then they're likely WR forks.
You'll probably need lighter springs regardless, coming from a 4-stroke, although the WR four strokes were the lightest of their class.

[jaunt]

48mm Closed Chamber KYB "S.S.S." forks came on:
WR250F 2015+
WR450F 2012+
YZ125, 250, 250F, & 450F 2006+ (RaceTech says 2005+)
YZ125X / YZ250X all years ('20+/'16+?)
Italian-built Husqvarna ('06-'14-ish, pre-rebadged KTM era)

The top caps on yours aren't fully recessed with bronze outer ring, so I believe these are open chamber forks, which are much easier to rebuild and easier to get valve plush then closed chamber / twin chamber SSS type forks. Since they are 48, I would think they might be off of 2006-2014 models that aren't included in the SSS list above.


Here's some good info about the top caps, photos to conpare yours:

https://www.thumpertalk.com/forums/topi ... -sss-fork/

Look up WR250F / WR250R forks '06-'14 & WR450F/R '06-'11, & that's my best approximation of what you have. I'm not sure if you would be able to tell what spring rate you have but the 450 is likely to have a stiffer spring.

www.RaceTech.com/ProductSearch is very useful in checking out types/sizes of forks, stock spring rates. Unfortunately it says "please call" in the information category for WR spring rates instead of an actual rate, when I browsed a couple years of 250R's/250F's. I use this all the time when looking at fork swap criteria / info.

Thanks for the info, yes I believe they are open chambers, they look identical to a WR that I've seen. This helps because I'll need to order seals soon. I'll probably just reseal them and try them out before jumping straight into a revalve.

[jaunt]

Couple more pics, they clear the tank and radiators just fine.

[SS109]

[Chuck78]

Try searching the ThumperTalk forum for KYB 48mm woods valving via Google, looking for Open Chamber / non-S.S.S. fork posts.

https://www.google.com/m?q=KYB+48mm+woo ... erTalk.com

These are fairly easy forks to rebuild and revalve, just watch some vids and read any posts you can find. Also watch a vid on revalving. KYB & Showa fork base compression valves will have a staked/peened shafts, so you need to file the end off of the fragile aluminum shaft to remove the nut. You might need to file into the nut slightly. Reinstall with low-medium strength loctite on clean degreased threads, and use a good inch pounds torque wrench to torque to spec, something very light like 6Nm
Use an impact gun to remove the damping rod bolt at the bottom, with spring still installed. It helps to break them loose on the bike with someone sitting on the bike to keep pressure on the internals so they don't spin. Oil will dump so be prepared with a drain pan.

[jaunt]

How its going, they are very easy to work on. I also got to use my coworkers fancy snap-on 1/4" torque wrench for the base valve nut, 46 in/lbs.

I'm also using dexron 3 ATF @ 120mm

[jaunt]

Update, took the bike for a little shake out ride yesterday, the forks feel amazing, very plush and compliant so far.

[jaunt]

Ready for a proper shakedown tomorrow, I'm excited to say the least.

BTW I used an OE 2004 CR250 front brake hose, it just barely fits with the enduro engineering hand guards on.

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[SS109]

Lookin' really good!

[KDXGarage]

Hell yeah it is! Congratulations on that sweet KDX.

[Ridea200]

I like it.

[jaunt]

Thanks guys, heres some action from Saturday, forks felt great, rebuilt engine with working KIPS feels incredible!

[KDXGarage]

You found some rocks!

[jaunt]

You found some rocks!

No shortage of those here in Colorado, lol.

[shmattym]

Awesome build. Looking for some info. I have a 2004 kdx220 and I’m looking to do this. I have a line to an entire front end from a 2012 kx250f with a front wheel. What’s everyone doing it seems like rb designs isn’t doing the swaps anymore. Someone help i want to get this front end if it’s going to work