Full Showa USD fork/RM125 shock conversion

Questions and comments about converting to beefier forks..
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Chuck78
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Re: Full Showa conversion

Post by Chuck78 »

SS109 wrote: 08:44 am Aug 20 2022 Yeah, XR400 is what my suspension guy said. For the record, I do have my forks slid up in the clamps by about 30mm IIRC. At 150lbs I would be running either .38/4.8 or .40/5.0 on fork/shock springs. I only went with .40's on the KDX forks because of having them slid up in the clamps so much but stuck with a 4.8 on the rear. BTW, I'm 140lbs.

@SS109, your initial mentions about the clevis swap said that it was a DRZ400 clevis, but every one after that from my searches, you said XR400.
I found a guy selling XR400 suspension, & he sent me a video with all sorts of measurements when I asked him for the clevis inside width. The XR400 was like 28.2mm inside width approximately (KDX is 22.7mm or so, RM has to be very similar), and a completely different shaft mounting type versus the RM and DRZ shock clevis.
I noticed browsing eBay that the DRZ400 clevis look nearly identical in every way to the RM clevis, and the XR400 was a completely different style.
From what I'm reading, the XR400 was relatively unchanged for its entire history 1996-2004 I believe. All the XR400 shocks on eBay have the same type of clevis and appear the same dimensions, and are all exorbitantly priced and not a parts shock price, all $300-$400!
DRZ400 seem to be more plentiful and available for cheaper. I know the engines were the same 1999 through 2020 or present on the DRZ400, also sold as a Kawasaki KLX 400 for a brief few years when Kawasaki and Suzuki were rebadging each other's models to save on production costs.
I'll review your photos again but I think maybe that first mention of it being a DRZ clevis was more correct, although it didn't look much shorter in length than the stock RM clevis.
I'll have an '03 RM125 here in the mail by Monday at the latest to compare. My buddy has a DRZ400 with a bad engine, I can go down to his farm sometime and check his out before buying cheapest DRZ shock on eBay.
Last edited by Chuck78 on 07:32 pm Aug 27 2022, edited 1 time in total.
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Re: H Series with Kayaba SSS fork assembly from a Yamaha

Post by SS109 »

That may be right, the DRZ. The big thing with the clevis IIRC was that it was shorter than the stock RM125 one. I'll try to pull some measurements from the one on my shock and post them up to help with your search.
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Re: H Series with Kayaba SSS fork assembly from a Yamaha

Post by Slick_Nick »

Chuck78 wrote: 09:39 pm Aug 24 2022
SS109 wrote: 08:44 am Aug 20 2022 Yeah, XR400 is what my suspension guy said. For the record, I do have my forks slid up in the clamps by about 30mm IIRC. At 150lbs I would be running either .38/4.8 or .40/5.0 on fork/shock springs. I only went with .40's on the KDX forks because of having them slid up in the clamps so much but stuck with a 4.8 on the rear. BTW, I'm 140lbs.

@SS109, your initial mentions about the clevis swap said that it was a DRZ400 clevis, but every one after that from my searches, you said XR400.
I found a guy selling XR400 suspension, & he sent me a video with all sorts of measurements when I asked him for the clevis inside width. The XR400 was like 28.2mm inside width approximately (KDX is 22.7mm or so, RM has to be very similar), and a completely different shaft mounting type versus the RM and DRZ shock clevis.
I noticed browsing eBay that the DRZ400 clevis look nearly identical in every way to the RM clevis, and the XR400 was a completely different style.
From what I'm reading, the XR400 was relatively unchanged for its entire history 1996-2004 I believe. All the XR400 shocks on eBay have the same type of clevis and appear the same dimensions, and are all exorbitantly priced and not a parts shock price, all $300-$400!
DRZ400 seem to be more plentiful and available for cheaper. I know the engines were the same 1999 through 2020 or present on the DRZ400, also sold as a Kawasaki KLX 400 for a brief few years when Kawasaki and Suzuki were rebadging each other's models to save on production costs.
I'll review your photos again but I think maybe that first mention of it being a DRZ clevis was more correct, although it didn't look much shorter in length than the stock RM clevis.
I'll have an '03 RM125 here in the mail by Monday at the latest to compare. My buddy has a DRZ400 with a bad engine, I can go down to his farm sometime and check his out before buying cheapest DRZ shock on eBay.
Are you the guy from ThumperTalk? I posted up a bunch of info on clevis' there.
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Re: Full Showa conversion

Post by Chuck78 »

@ Slick_Nick yeah that was me replying to the Thumper Talk post asking about the 2 different generations of RM125 Showa shock clevis hangers that the guy had posted a photo of side by side. Your info was very helpful, thank you sir.

@SS109 I replied here, but made a few more discoveries comparing this shock in my hands, so I deleted the post and will post on your original Full Showa topic since this thread was originally about what I believe to be the other best choice besides the Showa Twin Chamber forks, the 2006+ YZ250 KYB S.S.S. suspension.
Last edited by Chuck78 on 07:47 pm Aug 27 2022, edited 1 time in total.
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Re: H Series with Kayaba SSS fork assembly from a Yamaha

Post by SS109 »

It definitely was an RM125 shock body as he was going strictly off of what I told him would fit which is info I had gotten from here on the forum. Weird. Anyway, here is a sketch I did of the dimensions of the clevis I have.


Clevis KDX showa.jpg
Clevis KDX showa.jpg (53.15 KiB) Viewed 40156 times

About open vs closed chamber forks, the big place I notice the difference is on g-outs. A lot of times the closed chamber forks save me because the rain has cut a trench that I don't know about and then plow in to it. Closed chambered forks just seem to soak it up better and keeps from tucking the front and going over the bars. Same goes with racing terrain where I don't know what's coming next and all of a sudden come to a g-out at speed. Man, I love closed chambered forks in those situations!
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Re: Full Showa conversion

Post by Chuck78 »

SS109 wrote: 01:57 pm Aug 27 2022 It definitely was an RM125 shock body as he was going strictly off of what I told him would fit which is info I had gotten from here on the forum. Weird. Anyway, here is a sketch I did of the dimensions of the clevis I have.



Clevis KDX showa.jpg

Okay so those dimensions are exactly the same as the stock RM125 '01-'06 clevis... Except I believe you meant to type 22mm where you typed 21mm for the inside width. My '03 RM125 is 22.0mm, KDX '95-'06 is actually 22.5mm, so unless you ground down the rocker linkage / knuckle's inner bushing by 1.5mm (0.75mm per side), you must mean 22mm? Still, the KDX measures 22.5mm, a slight interference fit without filing/grinding 0.25mm off each side...?

What I determined more importantly when comparing all sorts of photos from eBay parts is that Don@ZR1 appears to have used the DRZ400 lower spring perch / seat, as it is about 5mm or even 7mm shorter height than the RM125's. The clevis looks identical to the RM125 unless the DRZ400 is in fact 21mm inside width but otherwise exactly identical.

Here's your final setup on the Full Showa thread, inner part of clevis beveled on a 45 degree angle to clear the KDX linkage rocker, also showing this spring seat is shorter than the stock RM 125, which appears to be identical to the DRZ lower spring seat perch:
IMG_20220827_144145~2.jpg
IMG_20220827_144145~2.jpg (907.43 KiB) Viewed 40153 times
That way Don@ZR1 could lower it for you internally without losing the softer end of spring preload adjustment range, or else needing a shorter length spring. That's the best I can figure out. I was going to post this on your original thread but you beat me to it.

Here's my '03 RM125 lower spring seat/perch collar vs an eBay DRZ400's (both nearly identical Showa 50mm piggybacks but DRZ reservoir is flipped):
IMG_20220827_152832.jpg
IMG_20220827_152832.jpg (359.25 KiB) Viewed 40153 times





@ SS109 - can you measure your lower spring seat height? It definitely looks exactly the same as the DRZ400. The RM 125 spring seat here measures 21mm as pictured:
IMG_20220827_164957~2.jpg
IMG_20220827_164957~2.jpg (686.67 KiB) Viewed 40153 times


I'm tempted to use a piece of 1/2" 6061 T6 aluminum plate and set it up on the lathe and cut my own custom lower spring seat that is 3/4" shorter, have the shock lowered internally 1/4" (I'd really want to make sure I had enough shock travel, need to figure out the stock leverage ratio for the KDX linkage), & swap out the stock 112.5 mm suspension linkage dog bones for something slightly longer (117mm stock KLX250 links) to both fit the longer motocross shock better without the rocker linkage topping out on the frame crossmember, as well as to both keep the suspension height reasonable but still about 5/8" (or 7/8" max) taller than stock for log/boulder clearance, and additionally to soften the MX compression valving, but not knowing what effect this would have on the rebound damping. I might be best off only running 1" or 1.125" lowering links at 117mm or 118mm to keep the valving closer to stock KDX (who knows what the RM125's leverage ratio actually is as well), and just run more race sag to keep the rear ride height where it needs to be to match the front end 98 RM125 forks slid up slightly in the triples,
Last edited by Chuck78 on 12:34 pm Nov 27 2022, edited 3 times in total.
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Re: Full Showa conversion

Post by Chuck78 »

I'm actually wondering, since the DRZ400 shock and the 01-06 RM125 shock are nearly identical (but the reservoirs are flipped, DRZ rez may not clear KDX frame), I'm thinking that perhaps the DRZ shaft itself may be slightly shorter as well as the lower spring seat? I would have to most likely buy one or drive an hour to my buddy's house to measure one to find out.
EDIT - I've got an ebay seller that may be able to get me a measurement this next week on the bottom of the clevis to the bottom of the sealhead, on the DRZ400 shock (his is an S/SM model). The '01+ RM125 measures around 8-3/4" there.
Last edited by Chuck78 on 07:49 pm Aug 27 2022, edited 1 time in total.
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Re: H Series with Kayaba SSS fork assembly from a Yamaha

Post by SS109 »

Interesting. He said he changed the clevis but maybe he meant to say the spring mount or maybe I heard him wrong. Hmm. Old age sucks sometimes.

The measurements I took above were with the shock still mounted so there is probably a small amount of error. I did no other mods to the clevis other than putting the 45 degree bevel on it. Anyway, I measured the collar like you asked. As close as I can get it it looks to be 14.25mm.

BTW, Donnie did not lower the shock internally at all. Every thing was external so it had to be with the spring mount/collar and/or clevis. He did not mention using a shorter shaft at all.
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Re: H Series with Kayaba SSS fork assembly from a Yamaha

Post by SS109 »

You know what, I'm going to move all these posts over to my original thread so that all this particular info is in one spot and we aren't hijacking soup-n-sandwich's thread any further.
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Re: Full Showa conversion

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SS109 wrote: 05:05 pm Aug 27 2022 Interesting. He said he changed the clevis but maybe he meant to say the spring mount or maybe I heard him wrong. Hmm.

The measurements I took above were with the shock still mounted so there is probably a small amount of error.
I measured the collar like you asked. As close as I can get it it looks to be 14.25mm.

BTW, Donnie did not lower the shock internally at all. Every thing was external so it had to be with the spring mount/collar and/or clevis. He did not mention using a shorter shaft at all.

Did you compare the length of the RM125 shock vs the stock KDX shock after Donnie was done?
I believe I read you stating it was a 1/4" longer approximately? Stock 01-06 RM125 shock is almost exactly 1" longer vs stock 95+ KDX.

The clevis you have is the same length as the stock RM clevis.
Your approximate spring seat collar perch cup whatever measurement is 6.75mm shorter than the stock '01+ RM125 part. But that doesn't affect the fully extended height of the shock at all, only spring preload adjustment.
So if the shock body itself is still stock dimensions and not somehow shaved down shorter & rethreaded (HIGHLY UNLIKELY!), then either the shaft must be shorter or the shock has an internal lowering spacer in it.

That makes me think that perhaps Donnie used the entire shaft and clevis assembly off of the DRZ400 shock. Perhaps it was a DRZ400SM (supermoto?) and it was a shorter ride height than the off-road model? I can't remember if the E or the S was the street legal model versus off-road model. Perhaps they are likely all the same height but different valving and spring rates.

98-00 RM125 also use a 50mm Showa piggyback, and it has the shorter spring seat collar cup thing like the DR-Z400 shock, although the part that the spring itself sits on looks slightly different and a hair taller. 98-00 only has one compression clicker, whereas the preferred '01-06 has the inner low speed compression flathead screw clicker adjustment and the outer blue anodized hex nut adjustment around the screw that is the high speed compression adjustment.
96-97 RM125 shocks "look" the same as 98-99-00, but are smaller piston/cylinder 46mm Showas, and definitely use smaller springs from what I can tell from part numbers and what I've read from people with hands-on experience.
98 was the last year that some of the springs came in purple, which is a big bonus for me... Although purple might be the optional "soft" 4.5 kg/mm vs the stock standard 4.7kg/mm, or perhaps they were all purple with the typical multi-colored paint marks indicating spring rate.
Last edited by Chuck78 on 07:57 pm Aug 27 2022, edited 2 times in total.
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Re: Full Showa USD fork/RM125 shock conversion

Post by SS109 »

The shock he built for me considerably raised the height of my KDX which, of course, works well with the 47mm twin chamber Showa forks. I did not ask him to make it the exact same length as the stock KDX shock but he might have done some parts swapping internally to get them closer to the same length. That said, I have no clue what he actually did inside.
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Re: Full Showa USD fork/RM125 shock conversion

Post by Chuck78 »

I'm 153lbs + gear + usually a 3.0L hydration pack in summer months, 1.0L of water in cooler weather.
Using Race Tech's spring rate calculator with inputs for the KDX220R, selecting options for singletrack riding, age 29-44 (I'm right at the upper cutoff there!), C class rider, who prefers soft suspension, Race Tech now tells me:

.35kg fork springs
4.57kg/mm rear spring.
I thought that was a bit soft, and I swear they never spec'd a spring that soft up front for me, their formula must've changed slightly? I didn't add the extra water weight I carry, or a pound for tools and tow strap etc.

Using all the same inputs except changing to B-class rider, Race Tech's calculator gives me:

.37kg fork springs
4.57kg/mm rear spring.

I thought that was odd that the rear spring wouldn't change when going to a faster more aggressive rider/racer classification?
I'm happily running stock 5.0kg KDX rear springs currently on both bikes, stock forks/springs with updated valving on the retired '99 220, KLX300R forks/stock springs on the '97 with stock rear shock/spring all freshly rebuilt. At first the KLX fork was an eye opener vs the stock sprung very plush KDX fork I'd been riding 7 seasons, noticeably firmer, but I grew accustomed to it on the gnarly trails and prefer it now, .37kg/mm I believe.

Anyways I wasn't expecting Race Tech to spec such a drastically softer rear spring, I figured a 4.7kg or 4.8kg would be sufficient, and was thinking .38kg fork springs.

I think going slightly softer than a stock rear spring and running .37kg fork springs will definitely be preferred for the worst of the worst nasty gnarly terrain that we ride in at our favorite trails in Southeastern Kentucky (Redbird Crest in Daniel Boone National Forest) and Southern West Virginia etc as well as a few gnarly spots in Southern Ohio and the Wellsville Ohio Forbidden Zone area.
Like 7:43 in this video, Trail 97 at Buffalo Mountain / Devil Anse (West Virginia):


I think that at my non-pro-level novice/intermediate riding level tackling gnarly rocky rutted steep terrain like that video (start it at 1:51 and check out that, Rockhouse Trail 199 is harder than these but this is a good example of the hardest of the hard enduro terrain that we'd typically ride), a 4.7kg RM125 spring with .37kg or .38kg fork springs in the Showa conventional twin chambers or these KX500 forks, with proper valving, will get me across this terrain with a bit more ease than 5.0kg stock KDX shock spring and .40kg stock RM125 Twin Chamber Showa conventional springs and woods valving.
Whaddya think SS109 & others? Is valving more critical than spring rate if I were to contemplate running .40kg stock RM125 fork springs after having a pro revalve the Showa 49mm Twin Chamber conventionals?

I ride my wife's 07 KTM200 XC-W with stock springs and 11psi on heavy duty tubes (vs my stock KDX shock and KLX300R fork, 90/100-21 fatty taller front tire and Neutech Tubliss @ 6-8psi rear 8-9psi front), and I cannot stand to ride even the normal rocky sections of the Redbird Crest trail for more than 30 minutes on hers without getting jarred to death and having a headache... wife and I weigh about the same, no wonder she gets tired more easily on the gnarly rugged trails! Plush is definitely where it's at in the nasty, but also we blast the gnarly choppy slightly easier stuff at 35-40mph frequently, and I still want to have the bike capably fit for the faster trails if we ride wide open areas. the high speed + low speed clicker adjustments on the 01+ Showa shock are a really nice bonus...
Last edited by Chuck78 on 11:20 pm Aug 28 2022, edited 2 times in total.
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Re: Full Showa USD fork/RM125 shock conversion

Post by Chuck78 »

SS109 wrote: 06:47 pm Aug 27 2022 The shock he built for me considerably raised the height of my KDX which, of course, works well with the 47mm twin chamber Showa forks. I did not ask him to make it the exact same length as the stock KDX shock but he might have done some parts swapping internally to get them closer to the same length. That said, I have no clue what he actually did inside.
SS109, assuming the KDX has an average linkage leverage ratio of 3:1 (I've read this is fairly standard for a lot of bikes???), & the fact that he used a shorter spring perch, Donnie must've lowered that shock some internally or used a shorter shaft if the DRZ400 shaft is shorter, as otherwise I'd think the shock would give the KDX CONSIDERABLE ride height increase to the tune of nearly 2"-3"...Being 1" longer shock length and using the same length clevis as the stock RM shock. That's why I think he used the shorter DRZ400 spring cup/perch/collar to compensate and use the stock length RM spring still despite the shock being likely internally shortened a bit.
But also, your shock is definitely a fair bit longer than the stock KDX from reading your past accounts, as I do remember you saying that you had to compress the shock 1/4" just to get it to install on the KDX.
I just threw my '99 220 with stock shock & stock 112.5 links up on a stand to get it at full droop to study the linkage.
Based on the fact that your '01-'06 RM125 shock after custom rebuild was still 1/4" too long, and looking at my linkage vs frame, tells me that your shock must still be fairly close to stock RM length, as a noticeably longer shock would in fact appear to push the rocker linkage into the frame crossmember that it mounts to, the KDX's frame would be the limiting factor on shock fully extended length.

I measured approximately 5-1/4" of exposed shaft on the RM125 2003 shock, versus just a hair over 5" on the KDX shock. I'm guessing that neither of them use the full shaft travel range at least I hope! Wouldn't hurt to do a mockup with a spring removed or just use 2 ratchet straps to fully crank down the KDX rear suspension to test this out before making any internal shock changes. If 3:1 leverage ratio is in the approximate range of the KDX, lowering the RM 125 Showa internally 5/8" or 7/8" should be no issue. But as they say, "to measure is to know."


I've actually been meaning to mark the shock shaft and use a ratchet strap to compress the rear suspension, with a tape measure in hand, and measure shock travel vs rear wheel travel, to give myself a rough approximation of the actual rear wheel/swingarm vs shock travel leverage ratio, for making rough guesstimated calculations on suspension alterations.

Honestly I'd really consider just leaving the shock a decent bit longer but running a lot more than the standard 100mm-110mm of rider sag when seated, just to get the geometry in the realm of where it needs to be to match a fork that's set up at 5/8" or 7/8" taller than stock and maintain somewhat proper steering caster angle. I'm thinking to lower the shock 5/8" internally perhaps, run a shorter (or custom) spring seat/perch/collar, and just back the preload off to achieve desired rear ride height.

I'm quite pleased with the revalved KLX300R fork / stock rear shock with 100mm sag set + low psi Tubliss, but I just can't leave any of my toys alone when there's other cool and significant improvements that can be made...especially when they will be of substantial benefit when riding the nasty gnarly terrain that I gravitate towards...
BuffaloMtnDevilAnseTrail97-August_2021.jpg
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Last edited by Chuck78 on 03:16 pm Aug 28 2022, edited 1 time in total.
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Re: Full Showa USD fork/RM125 shock conversion

Post by Chuck78 »

You know it just now occurred to me, I wonder what a set of Kouba KDX1 lowering links would do in terms of installing a stock length RM125 shock?
Heck, the compression valving might even be good to go for woods since a lowering link will soften the suspension action.
KLX300R dog bone links are longer than the stock 95-06 KDX, slightly shorter than the Kouba KDX1 links, that might be another interesting option.

But still I think one inch longer is a huge difference in terms of the shock length, but perhaps internally lowering just a hair (3/16"?) plus some KLX dog bones might even allow the stock shock's MX valving to do fairly well, in addition to not causing the bike to be 1.5"-2" taller in the rear or else having to reduce the shock travel 5/8"-3/4" out of 5-1/4" (overall available travel on the 50mm RM115 piggybacks is just a touch longer than the KDX shock by 1/8" or so).

A little bit of extra ride height can be very beneficial especially with the longer travel and softer suspension, for the gnarly singletracks. At 5'10" & 32" inseam, I've gotten quite used to the height of the KDX and have no issues with it being too tall vs my earlier years just starting out on riding dirtbikes more seriously in the woods. There have definitely been some times where I wished I had a skid plate, even with the KLX fork & it's stiffer than stock KDX fork springs, I've smacked boulders on the bottom of my frame pretty hard when riding at a moderate pace on the nasty stuff, not just coming down off of drops or anything that would compress the suspension substantially.

A bit more sag without compromising ride height also would benefit on the super gnarly stuff like trail 97 in that video @ 7:43, that would keep the tires in contact with the riding surface and allow the bike to move in a more linear manner while the wheels and suspension drop down into the voids and soak up the shelves/steps (as long as I can keep myself moving forward at 12 - 15 mph!).

Here's a breakdown on lowering links:

112.5mm long links = stock KDX links
117.0mm long links = ~1" lowered KDX = stock KLX250 links
118.0mm long links = 1.125" lowered = KoubaLinks KDX1
121(?)mm long links = 1.625" lowered = KoubaLinks KDX2
124.0mm long links = 2.25" lowered = KoubaLinks KDX3 ( = stock 89-94 KDX200 E-series links?)

I think running something in the range of 117mm to 118mm could possibly be the ticket here to fit the stock 01-06 RM125 shock more reasonably, and not go any longer than needed - with adjusting the race sag with rider seated or standing in order to correct front to rear ride height.
Racetech tells me for my weight I'd want 4.57kg rear springs, so running a 4.7kg rear spring and a 117mm lowering link and adding more race sag may get the spring rate right to that easily as well as softening the shock's stock MX compression valving.


judging by the 200lb RM125's rear spring rates ranging from 4.6kg, 4.7kg, 4.8kg, 5.0kg, and 5.1kg, I don't think the leverage ratios are going to be drastically different than a stock KDX's linkage/swingarm leverage ratios, so I think the 117-121mm range will work out fairly ideally.

I was actually looking at getting a set of 111mm KX100 stock links to use as lifting links to raise the rear of my other KDX to match the KX500 fork height, but that's probably a bad idea since technically the rear spring is already stiffer than recommended for my weight, although I do just fine with it with adequate race sag settings, but shorter links may push that out of my range.
Last edited by Chuck78 on 12:54 pm Nov 27 2022, edited 2 times in total.
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Re: Full Showa USD fork/RM125 shock conversion

Post by SS109 »

Just for reference, I'm 140lbs without gear, B rider/racer. I run .40 up front and a 4.8 in the rear and bottom out the shock at least once a ride. I normally run .38 springs up front but, due to sliding the forks up considerably in the triple clamps (EDITED: @20mm) with no internal shortening, I chose the .40's to help keep from bottoming out against the lower triple/fender yet my forks are still plush.

Man, you've put a lot of thought in to this. I just try something, or a variation of, what others have done. I wish I was more knowledgeable about the inner workings of shocks and forks but it's pretty much voodoo science to me. I do know this, springs are just meant to hold the bike up when combining the bike's and your combined weight and to hold the suspension in the proper starting point so the valving does what it should. Donnie valved my forks knowing I was going to run the stiffer .40 springs up front instead of my usual .38's. Everyone who has ridden my bike loves my forks including my buddy, Beers, who has the vaunted KYB SSS forks on his YZ250X. To me, valving is where the true magic is.
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Re: Full Showa USD fork/RM125 shock conversion

Post by Chuck78 »

Well... Since my "excellent condition" $188 '98 RM125 Twin Chamber Showa conventionals showed up with chrome pitting all over the seal travel range (seller refunded $68), & someone snatched up the '97 RM250 forks from Texas.Moto.Viking on eBay for $150 (deal! No triples but still a deal!), I found a set of 98 RM250 fork stanchion tubes for sale on eBay + shock parts to build my hybrid shock.

After seeing that 98-99-2000 RM125 models had a more basic version 50mm Showa piggybacks with purple springs on 1998-only, and shorter spring collar seats/retainers like the DRZ400 50mm Showas, I checked and this guy also had an RM250 purple 1998 50mm piggyback in pieces, which have 4.9kg/mm purple springs!
Image

I think with that shorter Showa 50mm spring retainer collar and a 4.9 kg spring on the KDX with some KLX250 steel suspension links (117mm vs stock KDX @ 112.5mm), think I might be right on the money here with softening the MXcompeession valving just a hair through linkage leverage changes, & slightly lessening the spring rate (RaceTech tells me 4.57kg ideal although that may be a bit soft? I'm pleased with the 5.0kg stock KDX springs with proper sag set). I'll give it a shot and see how it does for those swapped onto the 2001-2006 RM125 shock. It might not even really require any revalving, although I'm sure Donnie @ ZR1, Drew Smith @ WER, Jeff Fredette @ FRP, etc could definitely work some more magic on the valving to get them to perform better for my riding style. I'll likely buy a 2nd RM125 shock todothe same mods after this as well.

Also although most of the KLX 250 / 300 suspension dog bone links are thicker aluminum, a few years had steel links that look EXACTLY like the KDX. The aftermarket links work on all of them they say, but the bolts they have a different length of shoulder versus the ones that use a steel link like the KDX, so I'm not sure if the aluminum ones are compatible.

KoubaLinks reply to my technical questions and said that is uncharted territory for them, fitting a longer shock onto a bike using lowering links, but they said they would sell me theirs at wholesale cost if I wanted to try it out.
Not sure I care for the colors unless they offer different color options, which is not stated on their product pages.
Last edited by Chuck78 on 02:36 pm Aug 31 2022, edited 1 time in total.
'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
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Re: Full Showa USD fork/RM125 shock conversion

Post by Chuck78 »

@ SS109, you mentioned that you have your Showa Twin Chamber MX inverted forks slid up quite a bit in the triples, but you also said that this 2001 RM 125 shock raised the rear ride height considerably, to the point where it sounds like the dog bone linkage bottomed out against the frame in the top-out position when the redone shock still had 1/4" more extension to be had.
Is your bike ride height cranked up in the rear but nearer to stock up front? I'm just wondering what the overall balance is front versus rear ride height versus stock, it sounds like it might be sloped slightly towards the front, giving slightly steeper steering than stock?
Meaning for stock-ish geometry balance front and rear with slightly taller ride height.

Heading to Redbird Crest Kentucky for 4 days of gnarly rugged rocky trail riding in some big hills, sure would be nice if I had this Showa stuff ready to run! In time... Not much to complain about the current setup though, other than smacking my frame on boulders. I'll bolt on my skid plate before this trip...

So, the 01-03 RM250 has KYB shocks and forks in this era, but they look like they may stand a chance of fitting into a KDX in a similar fashion. And the clevis is already beveled on a 45° angle like you did SS109!
Length is uncertain, but like the 2001-2006 RM125 Showas, these also have two compression damping adjustment circuit clickers externally for high-speed and low-speed.


EDIT- 04-07 RM250 uses a 50mm Showa like the 01-06 125
2nd EDIT - 04-07 Showa 50mm RM250 piggyback shock has a noticeably longer clevis, so that would not work out well there's enough material that you could chop the bottom off and drill a new mounting bolt hole.


For a purple spring though, it looks like the Showa 98 RM250 spring and seat on an 01-06 RM125 Showa shock is the ticket!
'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
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'88 Suzuki Samurai TDI/Toyota swaps
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Re: Full Showa USD fork/RM125 shock conversion

Post by SS109 »

Chuck78 wrote: 11:29 am Aug 31 2022 @ SS109, you mentioned that you have your Showa Twin Chamber MX inverted forks slid up quite a bit in the triples, but you also said that this 2001 RM 125 shock raised the rear ride height considerably, to the point where it sounds like the dog bone linkage bottomed out against the frame in the top-out position when the redone shock still had 1/4" more extension to be had.
Is your bike ride height cranked up in the rear but nearer to stock up front? I'm just wondering what the overall balance is front versus rear ride height versus stock, it sounds like it might be sloped slightly towards the front, giving slightly steeper steering than stock?
Meaning for stock-ish geometry balance front and rear with slightly taller ride height.
I double checked my fork height and I measured them at 20mm (apologies! memory isn't as good as it use to be since my accident + old age). Setting it here is where I found the best balance between front and rear. I definitely didn't want the KDX turn any quicker than stock as they are already known for their super quick turning. On the rear, I was barely able to reach the recommended 110mm of sag with the lower spring retainer and stock RM125 length spring. Donnie said we can add a 5 or 10mm spacer if wanted to play with my sag setting some more but I haven't felt the need.
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Re: Full Showa USD fork/RM125 shock conversion

Post by Bogie83 »

So I’ve read all of the different rear shock threads, and I feel like everyone has made it sound way more difficult than it is. I’m literally in my shop now, putting my 2001 kdx220 back together. I picked up a 2001 rm125 showa rear shock. I beveled the clevis for clearance, and ran a file on the inside walls a couple times. And boom! She fits perfectly
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Re: Full Showa USD fork/RM125 shock conversion

Post by SS109 »

Bogie83 wrote: 04:59 pm Sep 05 2022 So I’ve read all of the different rear shock threads, and I feel like everyone has made it sound way more difficult than it is. I’m literally in my shop now, putting my 2001 kdx220 back together. I picked up a 2001 rm125 showa rear shock. I beveled the clevis for clearance, and ran a file on the inside walls a couple times. And boom! She fits perfectly
Yep, that's basically what I did. I just relayed the info told to me by my suspension guy. Hell, maybe he thought he did something and actually didn't!
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Current KDX: '98 KDX220
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