'96 RM125 forks onto '89 KDX200

Questions and comments about converting to beefier forks..
TheRadBaron
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Re: '96 RM125 forks onto '89 KDX200

Post by TheRadBaron »

Unfortunately I can't really comment on how the swap performs yet since I JUST got the bike running and I've only ridden it around the yard so far. I got really busy with work and the poor KDX got neglected for a while. I'm just waiting to get my carb from RB then hopefully I'll be able to take the bike out and put it through its paces. There's just not a whole lot to ride in my neck of central Illinois other than corn fields so it's a bit of a trip to get anywhere good.
The fork felt good around my yard but I've never really ridden any sort of modern dirt bike so I don't have much basis for comparison. I think they're considered pretty good forks so I wouldn't hesitate to do the swap if the price is good and you can get the necessary machining done. You'd need the front axle from the RM, too.
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Gotanubike
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'96 RM125 forks onto '89 KDX200

Post by Gotanubike »

So triples, forks, caliper, wheel(hub+rim) and front axle is everything needed, minus the machining? I'll see what his asking price is for the kit and caboodle. What is a reasonable price range to expect?
1990 KDX200
Bike Profile -> http://www.kdxrider.net/forums/viewtopi ... 61#p136315
Suspension Overhaul(Shock+89-92 conventional forks) -> http://www.kdxrider.net/forums/viewtopi ... 15&t=15255
96'-98' RM125 Showa 49mm fork swap -> http://www.kdxrider.net/forums/viewtopi ... 04&t=16994
KDXrider world map! -> https://www.zeemaps.com/map?group=186158
TheRadBaron
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'96 RM125 forks onto '89 KDX200

Post by TheRadBaron »

That sounds like everything that I can think of. I have no idea what price to expect. I did the RM swap because I already had the RM parts just sitting around. The KX fork swap is well documented and seems to be easier and potentially cheaper. I think you might be able to use the KDX front wheel but I'm not sure. I never really researched that swap. If you can get the RM parts cheaper than the necessary KX parts then I say go for it. If not, the KX swap might serve you better.
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Gotanubike
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'96 RM125 forks onto '89 KDX200

Post by Gotanubike »

$140 for everything sound pretty good? Sorry to barge your thread btw haha
1990 KDX200
Bike Profile -> http://www.kdxrider.net/forums/viewtopi ... 61#p136315
Suspension Overhaul(Shock+89-92 conventional forks) -> http://www.kdxrider.net/forums/viewtopi ... 15&t=15255
96'-98' RM125 Showa 49mm fork swap -> http://www.kdxrider.net/forums/viewtopi ... 04&t=16994
KDXrider world map! -> https://www.zeemaps.com/map?group=186158
TheRadBaron
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'96 RM125 forks onto '89 KDX200

Post by TheRadBaron »

$140 sounds like a pretty darn good deal to me. I'd go for it. No problem on the thread hijack, it's been inactive for a while anyway. Good luck with the swap.
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Gotanubike
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'96 RM125 forks onto '89 KDX200

Post by Gotanubike »

We agreed on $140 but I think he bailed on the deal because he hasn't responded. I thought $140 was a good deal, thing is I just finished rebuilding my factory conventional forks.

If he gets back to me I am definitely going to pick them up.
1990 KDX200
Bike Profile -> http://www.kdxrider.net/forums/viewtopi ... 61#p136315
Suspension Overhaul(Shock+89-92 conventional forks) -> http://www.kdxrider.net/forums/viewtopi ... 15&t=15255
96'-98' RM125 Showa 49mm fork swap -> http://www.kdxrider.net/forums/viewtopi ... 04&t=16994
KDXrider world map! -> https://www.zeemaps.com/map?group=186158
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Re: '96 RM125 forks onto '89 KDX200

Post by factoryX »

Had to do this when I did the swap on my 03 yz250 as well. Awesome. I'd say its worth it, the forks are awesome.
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Gotanubike
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'96 RM125 forks onto '89 KDX200

Post by Gotanubike »

I did it! Picked up my '97 RM125 forks tonight....I emailed the guy since June, I had second thoughts since I just rebuilt my stock '90 forks...

Thought $140 was too good of a deal to pass up. Luckily he still had them laying around...

TheRedBaron posted a lot of useful info here that I will need!

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1990 KDX200
Bike Profile -> http://www.kdxrider.net/forums/viewtopi ... 61#p136315
Suspension Overhaul(Shock+89-92 conventional forks) -> http://www.kdxrider.net/forums/viewtopi ... 15&t=15255
96'-98' RM125 Showa 49mm fork swap -> http://www.kdxrider.net/forums/viewtopi ... 04&t=16994
KDXrider world map! -> https://www.zeemaps.com/map?group=186158
TheRadBaron
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'96 RM125 forks onto '89 KDX200

Post by TheRadBaron »

Glad the deal ended up working out for you. I think you'll be happy with the swap. I've put some hours on my bike this year (though not nearly as many as I'd like) and I really like the way the forks perform. Again, this is the only "modern" dirt bike that I've ever really ridden, which is funny since it's an '89 but it's like a technological marvel compared to the bikes I'm used to riding. I'm sure that it would have felt like I was riding on a cloud even with the stock forks. I grew up riding twin-shock trail bikes with spindly forks.
But still, these forks seem like they perform really well. I did some research on them and I get the impression that they're truly excellent forks that sort of flew under the radar since they weren't USD and therefor "uncool". They're supposed to be better than most other forks available around the same time and for some time after.
Good luck with the swap.
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Gotanubike
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'96 RM125 forks onto '89 KDX200

Post by Gotanubike »

Awesome! Who makes em? They are Showas correct? Happen to know the spring rate of these?
1990 KDX200
Bike Profile -> http://www.kdxrider.net/forums/viewtopi ... 61#p136315
Suspension Overhaul(Shock+89-92 conventional forks) -> http://www.kdxrider.net/forums/viewtopi ... 15&t=15255
96'-98' RM125 Showa 49mm fork swap -> http://www.kdxrider.net/forums/viewtopi ... 04&t=16994
KDXrider world map! -> https://www.zeemaps.com/map?group=186158
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Gotanubike
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'96 RM125 forks onto '89 KDX200

Post by Gotanubike »

As it turns out they are Showa 49mm inner tube(previously mentioned here) with a spring rate of 0.40kg/mm. These are gonna be a huge step up from my dinky KYB 43mm 0.298kg/mm stock E series conventionals. Sucky thing is I just finished rebuilding them
1990 KDX200
Bike Profile -> http://www.kdxrider.net/forums/viewtopi ... 61#p136315
Suspension Overhaul(Shock+89-92 conventional forks) -> http://www.kdxrider.net/forums/viewtopi ... 15&t=15255
96'-98' RM125 Showa 49mm fork swap -> http://www.kdxrider.net/forums/viewtopi ... 04&t=16994
KDXrider world map! -> https://www.zeemaps.com/map?group=186158
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Chuck78
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Re: '96 RM125 forks onto '89 KDX200

Post by Chuck78 »

I, too, am wanting to keep the fancy Suzuki aluminum steering stems that come on these RM Showa forks' triple clamps...same as TheRadBaron.
I did a lot of measuring and thought it might work with milling that step off of the lower control, but that was still really pushing it.
I didn't really particularly like the idea of boring out the bottom of the triple clamps that the steering stem sits higher up in it, especially after reducing the height of the press fit area down to a standard triple, the RM triple is taller due to the raised step directly under the lower bearing area.

Well.... I revisited some of my fork swap info compiled for my vintage Suzuki street bikes...
I had a suspicion that turned out to be correct!

The RM Showa aluminum steering stems looked almost identical to this GSXR stem that I have here from some 1990s/2000's forks. Same as a Hayabusa steering stem. I was looking into a good steering stem to swap into a set of VMAX 1200 triples that will fit a Suzuki GS frame... VStrom DL1000 ran 43mm fork tubes as I desired for the GS750 & GS1000... Slightly less offset then a vintage 19" front wheeled street bike (I'm on 18's now) would typically have, but this seemed to be a bolt-on deal better than all the triples that came with the modern forks that I was looking at from bikes that primarily ran 17" sport bike wheels. One guy did it but said a spacer was required as the steering stem was longer. My GSXR stem looks identical and was the right size for the GS frames, not too long at all...



The deets:
$2.98 + shipping & I now have in my hands a non ABS model (older) V-Strom DL1000 lower triple clamp with an aluminum steering stem similar in appearance and identical and bearing size to the RM Showa stems and should be a direct swap, that is the exact length needed for the KDX frame!
...and as a bonus, the GSXR stem that I have (or the RM stem with the press fit area turned down shorter) will swap right into the V-Strom triple to work on my GS750 or GS1000 better for Bandit 1200/R6/GSXR1100K/RF900R fork tubes!


The KDX220 etc has around a 7-5/8" height from the bottom of the lower stem bearing seal up to the top of the upper bearing seal.
The "conversion bearing" size required will be 30mm x 47mm x 12mm, KDX frame upper is the height to fit up to a 15mm tall bearing.
The early (non-ABS, aluminum stem) DL1000 has a dimension of just over 7.5" between the bottom of the lower bearing press fit area and the top of the upper bearing seat area versus 7.625" on KDX stem/frame So this bearing that is 3 mm shorter height than the stock KDX bearing, will fit fully on the bearing seat area of the upper stem right up to the very top of the bearing area fit, & will fit the KDX frame perfectly with a 3mm tall x 30mm i.d. upper bearing spacer between the bearing and the dust cap seal, with the lock nut(s) above that.
The V-Strom I believe uses two thinner lock nuts with a toothed lock washer, instead of just one like the RM & KDX use. You can run either the double or the single RM lock nut. This works out pretty ideally because of the frame being taller, you lose some of the fork travel range on the non-inverted conventional fork chrome tubes and cannot slide the forks up in the triples ANY.
This setup will put both triple clamps closer to the frame which is definitely beneficial so that you don't have to push the fork tubes all the way down so the hex on the top cap is flush with the upper triple, just to get the full travel range back.
This will actually work out pretty perfectly based on where these RM 49mm conventional forks have witness marks on the chrome tubes where the triples were clamped for the RM's. The "12.2 inch" advertised travel is typical, the RM shows that fully extended with the fork sitting on the bench, there's about 11.6" real world travel based on examining the chrome in the entire seal travel range versus the 10 mm between the bottom of the upper triple and the marks, where I can see the seal stopped polishing the chrome on fork bottoming and normal travel. Their 12.2" of travel is the full range WITH the top out springs COMPLETELY COMPRESSED, which almost never happens in reality. Same as most bikes' advertised travel...
'97 KDX220R - purple/green! - KLX forks, Lectron, FMF, Tubliss
'99 KDX220R project - '98/'01 RM125 suspension, Titanium hardware, Lectron Billetron Pro, Tubliss
'77 Suzuki PE250 & '83 Suzuki PE175 Full Floater - restomod projects
'77 Suzuki GS750-844cc, '77 GS400/489cc & '77 GS550/740cc projects
'62 GMC 1000 Panel Truck
'88 Suzuki Samurai TDI/Toyota swaps
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Chuck78
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Re: '96 RM125 forks onto '89 KDX200

Post by Chuck78 »

These 97-98 RM Showa conventionals make the bike 5/8"+ taller than a stock KDX, which is a good thing for me even though I'm not particularly tall at 5'10", as I like plush suspension and I USE my Hyde Racing skid plate often - I need extra clearance over all the massive boulders in Southern Kentucky and Southern West Virginia! Add a taller more adjustable Showa 50mm piggyback '01-'08 RM125 shock also + KLX250 suspension dog bone links at 117mm vs KDX 112.5mm to balance it out.

If taller is not okay with you and you don't want to internally lower and reduce travel on the forks, then you want the 1996 Showa RM conventionals which are a bit shorter, or you want the 1999+ Showa RM inverted forks, as you can slide the inverted forks up in the triples without affecting the fork travel range, until the tire is going to bottom out on the fender at least.


One other discovery that I made, the 2001-2008 RM125 Showa 47mm Twin Chamber forks *may* also potentially fit directly into Honda CRF250X etc triple clamps without a stem swap for the KDX. CRF250X, R, & 450X/R also use Showa 47 mm twin chamber forks... I'm just assuming the clamping areas will be the same, I have not confirmed. The CRF & CR steering stems are taller than the RM stems... I haven't verified measurements, but I think an early 2000's RM125 47mm Showa twin chamber fork in these triple clamps could perhaps be one of the most ultimate setups If it worked out, so that you wouldn't have to do a stem swap even. Although looking at the YZ KYB S.S.S. forks, even with the same diameter chrome tubes, the aluminum outers / uppers had different upper clamping diameters 2-stroke versus 4-stroke for some strange reason. If the 47 mm RM versus CRF twin chamber forks have the same clamping diameters, then this would be a truly bolt-on swap with no stem swapping knurling pressing or bushing machining needed.

A few years of the 47mm RM Twin Chamber inverted forks actually use an inner chamber spring that is lighter than the CRF250X woods bikes, which means that with some revalving and springing the main spring for your weight, or if you are 175lbs or so already, the RM125 forks could pretty much be the perfect woods fork with just a revalving and no spring changes. Some models use a very stiff inner chamber spring which means the initial suspension travel is going to take more force to initiate travel. RaceTech and Cannon Racecraft both sell several different twin chamber inner chamber springs which are all lighter and are necessary for woods riding unless you already have something between 1kg - 1.2kg or 1.5kg (CRF###X models) that's conducive to a more plush suspension with a closed chamber fork, But a bit more prone to slight cavitation doing high speed whoops and other high speed riding.


The one thing that I'm learning though especially after peeling some of the carbon fiber wraps off of the fork tubes of these RM Showas, is that the 7000 series aluminum on all Showa forks seems to literally disintegrate when exposed to corrosive substances like salt, if the anodizing is damaged and missing in places.
I believe it's referred to something along the lines of integranular degradation? I guess this is really common on Showa forks when the anodizing gets damaged and salt or other corrosive contaminants get to the aluminum.
You really have to keep on top of it as it will spread if you don't completely sand / grind / dig it out and coat the metal.

My quest to run some of these RM115/250 49 mm Showa conventional right side up 49 mm twin chambers is turning into a really expensive one as I keep buying more forks only to find out they're beat to heck and have defects in the chrome tubes... 3 pairs of forks that all allegedly had good chrome, and I might potentially have one moderately usable tube out of the 6, and a lot of beat up worn aluminum outer tubes. All 1998 models, age didn't do them well... Sellers can either be flat out liars, or just incredibly ignorant about condition of mechanical parts and what to look for, including major eBay accounts specializing in bike dismantling...
OEM Cycle sold me two good tubes without the forks, the only intelligent and honest seller out of all of them. The guy from marketplace did tell me there were a couple minor defects but said he would be totally fine running them. That's the fork that had one tube that was pretty decent enough.
One other seller on eBay has a set with some fairly rough looking worn lowers but probably do actually have good chrome but for $340 some dollars with severe rubbing and wear from the brake hose routing on these things that is a problem always.

Well I just picked up a FOURTH set of these 49mm RM Showa 49mm conventionals now! They looked pristine and actually may be flawless except for the obvious severe corrosion on one of the bottom extensions on the lower tubes below the axle/brake lug. This integranular degradation or whatever it's called, it was PRETTY BAD on that portion despite the rest of the forks looking to be the best of any that I've acquired, but to get a good completely usable set of chrome tubes and good internals, it was worth the $199....
Surprisingly you can still get these forks from Suzuki if you want to drop $2,600! A lot of the parts are available internationally still even if they don't show up as available in the USA via Partzilla. RevZilla seems to show more available than Partzilla, although RevZilla is not usually where I go for OEM parts. CMS NL is the spot...half the stuff comes from Japan anyway when you order it from Partzilla. May as well just get it through the Consolidated Motorcycle Services Netherlands website...
'97 KDX220R - purple/green! - KLX forks, Lectron, FMF, Tubliss
'99 KDX220R project - '98/'01 RM125 suspension, Titanium hardware, Lectron Billetron Pro, Tubliss
'77 Suzuki PE250 & '83 Suzuki PE175 Full Floater - restomod projects
'77 Suzuki GS750-844cc, '77 GS400/489cc & '77 GS550/740cc projects
'62 GMC 1000 Panel Truck
'88 Suzuki Samurai TDI/Toyota swaps
'88 Toyota 4x4 pickup
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