Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Questions and comments about converting to beefier forks..
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Chuck78
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Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by Chuck78 »

For quite some time, the fabled 1996-1998 RM125/250 Showa 49mm right side up conventional forks have been on my radar, as many riders, especially older riders, regard them as perhaps the best woods forks of all time...(similar crowds amongst orange Austrian bike riders regard the 1998 orange bike 50mm conventionals in the same light).

These forks contain the same technology as a lot of modern forks still run (aside from the SFF separate function forks with spring in one leg and damping in the other, and the ones that run air springs with no steel coils - to save weight, I'm not a fan, even for my mountain bike bicycles...). Yet they are "right side up" conventionals which keep the chrome tubes more protected out of harm's way and are less prone to blowing seals literally annually....They are also the most burly and rigid/strong of nearly all conventional forks by their massive 49mm stanchion tubes... less flex, but still not the harsh rigidity of similar 46mm and larger inverted forks just by the nature of inverted forks being stiffer and less prone to twisting flex forces from the varied/rugged terrain. Too stiff of fork tubes and you will get the dreaded arm pump a lot more readily from tiring riding in rugged terrain.

Image



I've got both KLX300R 43mm inverted forks and 97-04 KX500 46mm inverted forks, but had never ridden Showa forks off-road yet. The KLX300 forks are an outstanding swap for the minimal effort as they are a direct swap and use the KDX wheel/axle, and suit a 145-165lb woods rider quite well with one rate stiffer on the springs stock and better valving stock (than a KDX's stock springs and compression valving), and the additional work to swap and re-valve and lower the 97+ KX500 open chamber KYB 46mm inverted forks is also a great swap, albeit significantly more work involved (+ more if using 96+ KX125/250 & KX###F forks which all require stem swaps & upper triple stem bushings custom made).

Fast forward a few years into running inverted forks on my KDX220R and my wife's KTM 200 XC-W... first off, replacing my buddy's KDX250 forks due to a tiny bit of rock damage on the lowers/chrome tubes was a bit frustrating - the tubes are significantly more in harm's way and are a critical sealing surface ESPECIALLY on inverted forks.
Then the blown seals ensued... I've spent far too much time using a SealMate tool (thin flat hook-shaped piece of flexible plastic), popping out the dust seals on the KLX and KTM inverted forks to attempt scraping out the residue buildup from the oil seals that causes weeping inverted fork seals perpetually... I've since learned that letting mud dry up on the chrome tubes and then riding them at all will jam some of the clay mud dust up into the oil seals to accelerate the amount of time until the inverted forks inevitably begin weeping and puking out fork oil...
Some people swear by various brands/styles of neoprene seal saver products that are a pre-filter sock that goes over the inner and outer tubes at the fork seal area in order to prevent dirt from ending up on the inner sealing areas of the oil seals causing leaks, but there are a lot of critics of these as they will require frequent removal and cleaning, otherwise they will hold in abrasive grit which will subsequently accelerate the wear on the chrome tubes in the travel range. There are sewn versions which must be slid on during fork rebuilds, there are velcro versions, and there are even zippered versions. None of these seem as good as just running right side up forks with accordian pleat fork boots aka gaiters.
The stock KDX forks with some very basic revalving (swapping out of some of the largest diameter compression stack shims) work great for casual woods riding, but some riders in rutted and rocky terrain cannot cope with the excessive underhang protrusion of the fork legs 3.5" below the axle, as this catches on roots/rocks/ruts substantially, and will throw the rider off track (or off the bike!) as bashing that part of the fork will give unexpected steering inputs to the front end... Others also complain that the stock 43mm conventional forks flex too much. On the opposite end of the spectrum, some riders say that inverted forks by the nature of their design, are too stiff and lacking in desirable flex, which will directly result in ride harshness in nasty terrain as well as riders experiencing arm pump. This inverted fork rigidity and resistance to twisting flex will also add slightly to the need for a steering damper in nasty rocky terrain...

This is what drove me to look into these somewhat legendary Showa 49mm conventional twin chamber Suzuki RM forks.

Image

I'll attempt to compile all the info I've saved on these things here in this space. I held off thus far because I didn't want to generate any additional interest in the form of competition for me trying to buy a better set off eBay when one may pop up... But at this point, I have 4 sets of the RM125W (W= 1998 model year) forks, and 2 spare chrome upper/inner tubes, and yet I still have ZERO chrome tubes that I consider great useable condition... 24 years of wear and tear has chipped and damaged the chrome on ALL of these parted out RM's chrome inner tubes, although I may have 4 tubes out of the 10 total that may be "useable" with some fine sanding / micro/spot wire brushing / acid etching & neutralizing / epoxy filling / fine sanding of the small gouges and rust pits... FRUSTRATING! re-chroming is available for around $585 shipped/taxed, and if you look in the right places, new OEM tubes are still available for $700/pair same as Race Tech charges for rechroming a pair of fork tubes. That's quite spendy unless you're okay having as much money into your suspension upgrades as a "good deal" (in the year 2022 at least) on a running riding rebuildable KDX...

I also have found that virtually all of these beautiful gold anodized Showa fork outers are made of 7000 series aluminum, which when the gold anodizing is chipped or scraped off, leaves 7000 aluminum very susceptible to some nasty corrosion from salt etc, which unlike 6061 aluminum, will appear to rot the aluminum to pieces in layers. Do a web search for "Showa corrosion" and you will find this all across the realm of dirt and street bikes running Showa forks, not just these Showa 49mm forks.
I believe from reading up on the DRZ400 forks, that scientifically, this is known as intergranular degradation or something to that effect. It is of utmost importance on these Showa Twin Chambers or the almost equally awesome and almost identical appearing (externally) DRZ400 49mm open chamber conventionals, that any of this Showa aluminum corrosion be sanded/scraped/wire-brushed out, neutralized, and then coated to prevent this from spreading like a disease. Brownell's Clear Epoxy paint (intended for firearms) has proven to me to be a great and tough single stage rattle can finish that I've used on shocks and street bike gas tanks (over top of single stage paint which is not gasoline resistant). I think this stuff or some Cerakote or other finish, or powder coating, would do really well to preserve these Showa outers.

I was reading up on 2005+ Yamaha YZ S.S.S. suspensions (and a few Kaw KX-F forks 2006+ which are also S.S.S.), and it is recommended that the closed chamber inner chamber seals on those things be replaced EVERY 6 MONTHS per RaceTech, WOW! I formerly regarded KYB S.S.S. forks as the best inverted woods forks one could have. I now think that for woods riding with some more favorable traits for high speed whoops type riding etc as well, running Showa Twin Chambers with the lightest inner damping chamber blow-off springs available, 1.0kg Racetech or 1.2kg/1.6kg progressive rate Cannon-Racecraft inner chamber springs, may top the KYB S.S.S. if this 6-month S.S.S. inner chamber seal life is in fact true. The Showa Twin Chamber inner chamber seals also do wear out in time and leak into the outer chambers of the forks (where the oil for lubricating the fork slider bushings is), but 6 months... wow.



So obviously you may be wondering why the more modern closed chamber (also referred to as twin chamber) forks are "better?" Well, it depends on the rider's choice of terrain, skills, and riding style, as to whether or not the more advanced nature of these forks is beneficial or even noticeable, but the twin chamber (closed chamber) design is more resistant to cavitation on higher speed riding sections.
Cavitation is when the fork oil gets blended with the surrounding air or nitrogen charge inside the suspension assemblies, from washboard sections and whoops or more particularly, aggressive high speed riding through these conditions resulting in a lot of deeper fork travel movements in rapid succession. Cavitation completely alters the viscosity of the suspension oil, as it becomes an emulsified mixture of oil and tiny air bubbles, which will also completely alter the damping rates on both compression and rebound. A design that resists cavitation will thus provide more consist damping traits when the rider is blasting through a lot of rough terrain or whoops with great speed. The tradeoff is the initial plushness of the forks.
The inner chamber springs on the damping assemblies add resistance to the initial suspension travel movements, so this will take away from the plushness of the suspension's initiation of movement and damping slightly. Some of the Showa T.C. motocross forks come with quite stiff internal chamber springs (2.4kg/mm or even 2.7kg/mm) to very strongly resist cavitation before the spring allows the compression valving assembly to blow off as far as I how I understand it's terminology in the TC's.
It is very possible to make these twin chamber forks quite plush however. The Honda CRF250X and CRF450X models are a 4-stroke woods bike version of the motocross bikes ending with the R designation, and these bikes also run a much more plush version of the 47mm inverted Showa Twin Chamber forks, and these bikes run 1.5kg/mm inner chamber springs. Many people say these bikes are quite plush, although I have read of a few complaining that they still want something more plush than the stock X models offer.
Race Tech's page for inner chamber springs recommends their lightest offering, the 1.0kg/mm inner chamber spring, for a 160lb woods/enduro rider for both Showa Twin Chamber and KYB closed chamber forks. I believe that this 1.0kg/mm inner chamber spring + premium SKF low-friction seals or the even better dual compound SKF seals for 49mm Showas + correct spring rates per rider weight (.38kg Cannon-Racecraft main springs for me @ 154lbs) will in fact result in a fork that can be nearly as plush in the rocky rooty rugged nasty terrain as plush-valved open chamber forks, but also will be better at providing more consistent damping than open chambers when maxed out in the fast whoops and riding quite aggressively at higher speeds inducing lots of suspension travel in rapid succession.

HOWEVER.... just because these forks are more modern technology, and "better," doesn't necessarily make them "better" and beneficial in any noticeable way to many casual woods riders, or riders who only ride primarily in the slow rocky nasty terrain. There is something to be said for a good properly valved / properly sprung open chamber fork, even the older more basic versions with just a base valve and rebound valve and no compression damping floating mid-valve on the underside of the rebound piston. These basic old school open chamber forks, like 1991-1994-ish KX125/250 inverted forks, KLX300R forks, 1988 and/or 1989 KX conventional cartridge forks, and the stock 1995-2006 KDX forks are rather easy to set up very plush for casual trail riding or even for nasty rocky rooty rugged technical terrain... One doesn't necessarily need the cavitation-resistance of the closed chamber design if they aren't blasting whoops and other sections at excessively high speeds. In that case, I would steer towards 2000-2022+ DRZ400 49mm Showa open chamber conventionals as being the "ultimate" woods bike fork swap for someone wanting conventionals. They are notoriously plush and awesome in their valving, and about as rigid in terms of twist/flex as one would want in the woods without going to what some consider harshly rigid and twist/flex resistant in the fatter tubed inverted forks...


(*bike photos above with the 49mm RM Showa forks are borrowed from elsewhere on this forum! NOT MINE! I'll add photos of mine in 2023 after some winter shop work getting the triples machined for the stem swap, and rebuilding/revalving a set of these for woods)
Last edited by Chuck78 on 10:54 pm Nov 20 2022, edited 5 times in total.
'97 KDX220R - purple/green! - KLX forks, Lectron, FMF, Tubliss
'99 KDX220R project - '98/'01 RM125 suspension, Titanium hardware, Lectron Billetron Pro, Tubliss
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Re: Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by Chuck78 »

So the 1996 version RM125/RM250 Showa 49mm conventional twin chamber forks do have a bit more underhang below the axle than the 97-98 versions (still SIGNIFICANTLY LESS than the stock KDX forks), BUT at a tradeoff... if you want the full 11.6" of effective travel (12.2" advertised but as with any bike, that is a stretch as it includes unnaturally topping out/compressing the top-out spring FULLY), the 97-98 versions will make the bike around 1-5/8" or more taller than stock, whereas the 1996 RM125/RM250 versions with the greater underhang will allow you full travel AND somewhere nearer to the stock KDX's ride height...

So the 97-98 versions will either need internally lowered which reduces the travel (to basically the stock KDX 11.6 inches *ADVERTISED travel* + sliding the forks up through the triples 5/8" or so additionally to fine tune), or else your bike will ride like a slow steering raked out chopper unless you put on a longer rear shock or else make up some custom 109mm or 111mm suspension dogbone links, the opposite of a longer lowering link.

Stock 1995-2006 KDX suspension links are 112.5mm. KX100/KX85 links are 111mm but smaller bolt holes so they'd need drilled out, and perhaps slightly offset-drilled to shorten them a small amount, FYI!

Although this will alter the leverage ratio against the shock slightly, and firm up the suspension a bit, I believe this will result in leveling out of the ride height when installing taller forks. I devised this when looking at my taller KX500 forks after seeing that I can only slide them up so much in the triples before risking bottoming out the front tire on the triple clamp/fender bolt area. Also one could run a taller fatter 120/100-21 rear tire and stock height 90/90-21 or same height skinnier stock 80/100-21 front tire.

The other thing which I have learned from SS109 and a few others posting on this forum, is that the 1" longer RM125 Showa rear shocks can also make a really good match in height to the taller fork swaps. 1997 & a few years prior RM125 use a 46mm Showa piggyback similar to the KDX shock but longer. 1998-2000 RM125 use a 50mm Showa piggyback shock. These can be spotted out by the bottom part of the lower spring seat having a widening taper on vs a straight cylindrical lower piece on the pre-98 models. 1998 has a PURPLE spring on the RM125 and RM250 Showas! Bonus for me aesthetic goals! 4.7kg/mm on the RM125 and 4.8kg/mm on the 98 RM250 (*NOTE - RM250's jumped back and forth between Showa and KYB throughout the years, but RM125 2-strokes were always Showa from mid-90's to the very end of Suzuki 2-stroke RM's in 2006 or 2008).
Soooo.... the 2001-2004 RM125 (05-08 RM125 & RM250 Showas have longer clevis that needs shortened, 01-04 RM250 used KYB not Showa, FYI), 1st half of the last generation of '01-'08 RM125 2-strokes, also used a Showa 50mm piggyback shock that was 1" longer than the KDX200 H-series shocks, BUT...the 2001-2004 shocks have both a "high speed" and a low speed compression clicker adjuster which is actually more like the base valve in forks, a seperate shim stack assembly in the top of the shock body. As stock, the high speed is more of a mid speed compression adjustment, but aftermarket compression adjuster assemblies alter that. Extra on the fly tuneability if this sort of adjustment is something that you may want to have for adjusting the clickers for varying riding area terrains. In addition to the standard compression clicker adjustment screw by the piggyback reservoir, there is an outer blue anodized hex adjustment additionally, whereas the 2000 & older have just the hex thread to thread the entire thing into the shock body, no adjustment other than the single compression screw clicker.
Showa49mmRM125.jpg
Showa49mmRM125.jpg (192.77 KiB) Viewed 5728 times
So these shocks being 1" longer will CONSIDERABLY RAISE the rear of the KDX. Let's look at how to lessen this and get it to a minimal suspension lift for those of you who are taller, who are okay with tip-toeing, and/or who need the additional ground clearance for big boulders and log hops like myself 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 riding at Redbird Crest and Buffalo Mtn / Devil Anse and Rockhouse trails.
:supz:

KLX250 steel suspension links @ 117mm long vs the H-series KDX's at 112.5mm are effectively "lowering links" for a stock KDX at around 1" lower ride height, also altering the suspension leverage ratio slightly (softer, which may be a good thing for running an RM motocrosser's shock valving - RM may have more leverage ratio than a 95+ KDX anyways as the shock springs are in the 4.6kg-5.2kg range vs a KDX "woods bike" stock rate @ 5.0kg). I haven't done this install yet, but I think the stock RM valving may perhaps work out to be softened good enough with the longer 117mm links.
RaceTech specs out a 5.0kg shock spring for me if I select "1-inch lowered" vs stock ride height they spec a 4.65kg shock spring.
Also of note - most of the KLX300's seem to have thicker steel-bushed aluminum suspension dogbone links. These work on the '95-'06 KDX if one is to also use the longer linkage mounting bolts from the same KLX300 model. Also, these lowering links can easily be fabricated at home out of 1/4" bar stock steel which is almost the exact thickness as the steel metric links on these bikes.

Although I question Race Tech's recommendation after being 154lbs & running the stock 1995+ KDX's stock 5.0kg shock springs in the woods with proper 100mm+ of rider sag set, but Race Tech's calculator tells me I need a 4.6kg shock spring for singletrack/enduro trail riding for a 44yr-old C-class or even B-class rider preferring soft plush suspension... Well, the purple 1998 50mm piggyback RM125 shock springs are 4.6kg/mm, '98 RM250 @ 4.8kg, so I guess I'll dial in the sag and rear ride height properly and see how the purple '98 RM250 spring does on my purple & green '97 KDX220R as well as on my '99 220... The 98 RM250 shock springs are also purple, and I think a bit more suited for my purposes at 4.8kg/mm.
UPDATE! I picked up a lightly used RCS / Renton Coil Spring 4.9kg Titanium shock spring for 50mm Showas, 2lbs weight vs stock RM250 4.8kg spring @ 3lbs!
Diverse Spring no longer makes Titanium shock springs due to slow sales because of the high cost, but sell a 4.8kg & 5.0kg Superlight Silicon-Chrome spring that weighs 2.5lbs @ $119.99 vs RCS Titanium shock springs @ $499 new...
OEM Yamaha springs were available in 46mm KYB S.S.S. shocks for several years also, but they're smaller and reportedly not as durable of a titanium alloy, with a few sporadic spring failures.


Also noted, in the picture above you will see extra 2-piece lower spring seat parts sitting next to the shocks. These are 1998 RM125/250 lower spring seats from Showa 50mm piggybacks, which are slightly shorter in height than the 1999-2000(???) & 2001-2008 RM125 Showa 50mm piggyback rear shocks' seats. If you find the need to lower these shocks internally in addition to the KLX250/KLX300R links used as KDX lowering links, these lower spring seats will be very beneficial to help keep the threaded preload adjuster in the middle of the thread adjustment range, or also to allow additional suspension sag as desired.
SS109's suspension guy, the legendary Don/Donnie at ZR1 Suspension in Arizona, is the one who discovered these shorter Showa 50mm lower spring seats/collars are beneficial in swapping onto the 2001-2008 RM125 shocks when adapted to the 95+ KDX's. Disregard a mention of being an XR400 spring seat, that was an error, DRZ was mentioned in other posts which we've cleared up. XR400 used KYB shocks whose spring seats aren't compatible with this Showa adaptation.

DRZ400 rear shocks' lower spring seat pieces are actually identical to those 98 RM lower seats. The DRZ400 shocks themselves are actually nearly identical to the 2001-2008 RM125 shocks here with the low speed + high speed compression adjustments, BUT the DRZ400 50mm Showa's piggyback reservoirs are clocked differently and I do not believe their reservoirs will fit in the available space on a 95+ KDX, however 89-94 KDX200 owners may want to look into this reservoir placement, as it may be viable on those bikes which use a different rear shock body than 95+.

Image

Also, SS109 had noted that the RM's lower shock clevis has to have a portion of the center cutout's edge on the clevis beveled at a 45 degree angle slightly in order to clear the KDX's rocker linkage without bottoming out on it, as you can see in his photo above. I believe he also said he very slightly ground on the KDX's rocker linkage as in the photo below, where the clevis's edge (now beveled) would otherwise make unwanted interference contact when topped out I believe.

Image

He is also running stock links with his RM125 Showa shock which gives considerably taller ride height over a stock KDX, and his shock actually had to be compressed 1/4" to install into the KDX as it was topping out the KDX's suspension range at that even, rocker to frame. This is why a slight bit of internal shock lowering will be beneficial. I plan to remove the stock shock completely, with the bike up in the air on a stand, and measure the available height for the shock with the suspension topped out, see if it changes any with the KLX250 117mm suspension dogbones installed, and then internally lower the 2001-2008 RM125 Showa shock accordingly to that measurement.
Last edited by Chuck78 on 12:03 pm Jan 03 2024, edited 8 times 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
'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: Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by Chuck78 »

Also of noteworthiness for woods riders looking for additional protection from rocks and boulders, the identical appearing but open chamber 49mm Showa conventionals found on the DR-Z 400 also have available a Maier fork protector / disc guard combo which also perfectly and exactly fits the 97-98 RM125/250 forks, and can fit the 96 for the most part with a bit of trimming to the bottom portion on the non-brake-side-only, although this will leave just a slight bit of the underhanging tubes exposed on the 96's non-brake side, easily remedied.

Here's the DRZ400 Maier disc guard / fork protector, perfect fitment and exacting fitment on one of my 98 RM125W forks...
Showa49mmRM125-DRZ400Maier_guard.jpg
Showa49mmRM125-DRZ400Maier_guard.jpg (109.71 KiB) Viewed 5718 times
These gold anodized Showa forks are a beautiful thing (in good condition at least), but protection of the aluminum lowers is critical at least in the form of some clear or black vinyl or "carbon" fork wrap protectors, or a clear coat epoxy paint layer at minimum in order to prevent the dreaded Showa 70000-series outer fork tube corrosion when the anodizing gets damaged and allows salt etc to contact the bare alloy. If one really wanted the ultimate in protection, the DRZ400's accordian plate fork boot gaiters and the OEM plastic clamps to secure them onto the lowers will offer additional protection to these forks, and in addition to the Maier guards, both are picture below (available in white, carbon fiber, and black).

Image


Suzuki also offered optional 97-98 RM fork lower guards left and right and a disc protector. Most are yellow but 98 also had grey plastic versions available. I never found one listed in the parts fiches, but apparently 98 also had a separate grey plastic rotor guard as well, as I have one in my possession from one of the 4 parted out 125's which I got the donor "parts forks" from. 96 had different lower guards that mounted around the axle lug area and below, which shows to me that Suzuki realized the extra underhang of the 96 models was more prone to smacking into rocks and ruts. Unfortunately, I have not been able to locate any remaining stock anywhere of the OEM brake side lower fork protectors, but the non-brake sides are still available in both yellow and grey plastic.



Another note is that I believe the 95+ or 93+ KDX brakes (and probably 1990's KDX250 brakes?) will bolt up to these forks, although you'll need to check the centering of the caliper over the rotor. It has been stated by canamfan that one very thin washer was required under each caliper mounting bolt to attain perfect centering of the caliper over the rotor. This may vary with every individual bike setup depending on what wheel + axle + axle spacer(s) you are using, but canamfan's I would guess pertains to running the stock RM wheel and spacers/axle intended for this fork. I will likely be using a KX wheel with custom axle spacers for mine, as I have it, and it fits KDX rotors which I have a few of (the 96-98 RM rotors do look very cool though!).

Also of note, the Maier fork/disc protector picture above shows a 2000-ish KX125/KX250 wheel installed on a KX axle in the RM forks. The axle spacers are not right, but otherwise these can be swapped with some custom spacers made or longer 20mm axle diameter spacers ground down to proper length. A belt sander table with use of a set of micrometer calipers to check squareness of the cut throughout the process can be used to resize axle spacers, but you lose any larger diameter flanges on the ends of the spacer when going this route. Often the parts fiches will tell you the length of the spacers, so it's possible to browse different bike models that use 20mm i.d. axle bearings and 20mm o.d. axles, and find some mix and match spacers to make your KX wheel work if you happen to have one or don't have luck finding a good 96-98 RM front wheel. The same wheel may possibly interchange through the 99 and 2000 models also, which are technically of the same generation of RM models 96-00, although they used 49mm inverted Showa Twin Chamber forks in 99 and 00. Still a good swap but suffering from some of the same issues, 20-22 years old and showing their age from use and abuse, as well as only 2 years of parts interchange on a lot of the parts.
Last edited by Chuck78 on 12:06 pm Dec 06 2022, edited 5 times 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
'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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Re: Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by Chuck78 »

MASSIVE INFO DUMP OF ALL MY COMPILED NOTES, I will be editing this as time allows:






Subject: 96-98 RM 49mm Showa Twin Chamber forks

Fork identification externally '96 vs '97 vs '98:
*'96 had more 20mm lower overhang (underhang) & a hexagon cap, and are shorter overall length. The top caps had a blue circular area directly surrounding the center damper adjustment screw, 97 was aluminum color.
*'97 had less lower overhang (underhang) & a hexagon cap that was all aluminum in color vs 96 blue center, & forks are taller than '96.
*'98 had same minimal underhang as '97 but the more current slotted top cap with only two wrench flats all the way across the top diameter (& a more subtle shorter hex on the outside diameter) vs. the hex,
& taller overall length vs '96 (similar to 97 but perhaps not exact???). '98 forks have 2 faint grooves machined around the outside lower fork leg just below the seal (externally), '97 does not.


The upper bushing in the aluminum half just below the seal is a thinner wall bushing than a '97. A '97 bushing wont fit in a '98 leg and a '98 will fall into a '97.
NOTE - fork bushings show NLA for 96-97 via OEM except from CMSNL.com, but ebay has a multitude of aftermarket kits (-Chuck)
The chrome damping rod is 10mm diameter on a '98 (& 10mm on a '96), vs. 12mm diameter on a '97
The spring collar/seat (what the spring sits on) is plastic with aluminum sleeve at(and?) the 97 has thin walled aluminum (which can crush/collapse under heavy bottoming)
The lower rebound adjuster base nut is a smaller diameter than a 97.
(-negativenoel on KDXRider.net)


98's work just that little bit better and have a quick change high speed valve assembly as do all inverted Showa Twin Chamber forks 1999+) for valve shim tuning without tearing down the entire fork - to access, hold the octagonal outer nut on the top cap with a large wrench and use a smaller wrench or special socket to unscrew the raised slot/flats center portion. Pull hard, as suction holds it in. You can put a racetech gold valve on but you don't have to bother pulling the mid valve apart, and DO NOT use the mid check valve conversion if supplied by racetech.
I suggest single stage valving as its more predictable through the entire stroke.
I've used 97 lower legs on 98 internals on a 2015 wr 250
Best advice on twin chamber / closed chamber forks is to use low stiction SKF seals on these forks
(-negativenoel on KDXRider.net)



Schematically, there are only minor differences between the '97 & '98 fork, although a majority of the parts carry different part numbers. In the '97, there's a 2-piece plastic collar that is 1-piece in the '98 fork.
The '97 forks are vastly different than the '96 internally.
'97 forks use a 12mm damper assembly rod, whereas '96 & '98 use a 10mm damper assembly rod.

'96's work very well on a woods bike with shorter fork height and slightly shorter travel range like a KDX, as the '96 are shorter and likely will not need lowered. The '96 also can be lowered substantially for use on vintage bikes with shorter forks, by simply using '97 springs in them (449mm vs 518mm length) and corresponding length difference of top out spacer in the cartridge to lower them and take up the slack, which works well to reduce to 9.5" travel for the 1977-1986 2T enduro bikes like the Suzuki PE, Kawasaki KDX, and Yamaha IT.

This era of Showa Twin Chamber 49mm conventional RM forks are very highly regarded amongst old school woods riders for swaps onto other bikes, & are highly tunable for mixed riding in order to be able to handle the slow technical rugged terrain as well as higher speed whoops and dips

From Heart_Of_Darkness on Vital MX:
The stock pistons have large ports, they're not a restriction. Absolutely don't run the inner chambers low on oil, but you can vary the oil height of the outer chambers.

(******** I've been reading about Twin Chambers & cavitation vs plushness, ReStakor has amazing writeups about this - but it seems as if you can get away with a softer TC ICS spring if yourbase valve ports are shaped in a way to minimalize cavitation - so perhaps the FMGV 2320 (97-98) & FMGV 2040 could still perhaps be beneficial? I'll have to tear a pair of these down to check the stock port shapes soon. See ReStakor cavitation article later on in this thread)


A good woods re-valve is a two stage base with greatly softened high speed, a somewhat softened mid with a float in the .25-.30 range, and correct rate fork main springs with minimal preload (there's a lot of preload from the factory).*************************************(great info here!)

*****Check those forks (you'll need to disassemble them) to see if the bottoming cup at the base is installed correctly. If it wasn't (and it's easy to not install it correctly) then the damping rod cartridge hammers it every time the forks compress. I had a set that happened to. It's very dangerous if you don't catch it. (-gotanubike on KDXRider.net)



Some have used this thread on DR-Z 400 49mm open chamber conventional fork valving as a basis for the Showa 49mm twin chamber valving on the RM fork swaps, although if the compression piston diameters are different, the valving is likely not going to be directly compatible without some adjustments for the added flow of a larger piston etc:
https://www.thumpertalk.com/forums/topi ... ns/page/8/

also look at the Thumper Talk thread with a subject/title regarding How to make Showa Closed Chamber forks plush for woods riding. I'll post that link later if it's not in this jumbled aggregation of my notes elsewhere already.

------------

Drop the oil level down quite a bit lower then what RT recommends for the RM twin chambers, and work your way up. Measure your fork springs as my set had negative preload and if you do too then make some spacers to bring it up to 0-3mm.

I don't do desert riding so I'm not familiar with the stock valving. You could try stock and see how it goes as a lot of people like the stock setup.

I'm running this right now for woods but I'm always playing with the base/mid.

20X.1

18X.1
16X.1

14X.1

13X.1
12X.20

11X.20

11x.25
11.35X.40

Rebound - Stock
Midvalve
20X.1 (3)
08X1.35 (collar)
11X.20 (2)
Float - .0mm

---------

------------------
Jeremy Wilkey
Owner, MX-Tech
Oct 28, 2003
#2
Lew,
These babys are weird and really need some special tools that ESP has pretty cheap. While its possible without them, I would never want to EVER, and I know you know the value of the right tools. *****They can be trashed in about 1 second when you go to put the lower spring set if its not aligned with the oil lock. These are actually are set by oil height, not volume. See if you can get those tools and then lets talk.
-Jeremy 

(note - gearheadE30 who has the very informative YouTube videos of comparing and tearing down these forks comments that these forks are incredibly easy to work on, contrary to what the professional suspension tuner Jeremy Wilkey says above)

-------------------

Drew Smith @ WER Suspension (2011 from Cafe Huskie forum):

I have had quite a few customers that really cling to the conventional forks, mostly the 49 mm Showa (RM). The condition of the rubber seals that keep the oil in the inner chamber are of concern to me because of the age of these front forks. We had some replacement seals made by a small volume (made in U.S.A.) seal maker. they are good but I'm concerned that they add some friction at the cartridge rod. All of this leaves me feeling like my customer might be spending for not so good value.
I like the very similar appearing 49mm conventional Showa open chambers that come on the DRZ-400. We have some very good settings for them. I believe the root of this discussion centers around the benefits of the additional flex provided by the conventional design. Also the fact that conventional forks hardly ever blow seals, whereas inverted forks below seals out at least once a season because they are more exposed to mud.


***I believe Drew may be referring to this:
Showa Genuine Parts
Gas Seal Free Piston 10 x 20.2 x 5mm
Showa Genuine Part
SKUF32201002
https://www.teknikmotorsport.com/F32201 ... 0.2-x-5mm-
RaceTech also has this on their product page as FSTC RS1020
https://racetech.com/ProductSearch/12/Suzuki/RM125/1998

perhaps these were very tough to track down at one point in time as of his 2011 comments above, but they seem to have readily available replacements at present if this is the seal he was referring to.
F32201002b.jpg
F32201002b.jpg (90.82 KiB) Viewed 4690 times
F32201002.jpg
F32201002.jpg (91.87 KiB) Viewed 4690 times
The Teknik Motorsport page shows a NOK brand seal in the picture with the part # AR0258. I cannot see any additional characters beyond that, but a web search brings up AR0258E5, and calls it a dust seal. No returned results without the E5. Perhaps this is the same, or could be a totally different application and only shares the same first 6 digits due to size. It also seems to have two thickness or height dimensions, 5mm and 7mm, so without tearing down the forks, I'm not certain if it is both (seal lip protrudes an additional 2mm?), or if that E5 seal is just something completely different.
I may have to just order some from Teknik or RaceTech to find out for myself. These don't seem to show up in the Suzuki parts fiches, but seem like quite an integral part of doing an annual fork servicing, especially considering the KYB S.S.S. forks' similar inner chamber seal is recommended to be replaced EVERY 6 MONTHS!!! Wow.

Searching ebay for 10x20 seals brings up a lot of options, adding Suzuki or Kawasaki to the search only returns water pump seals and outboard boat engine seals. I am guessing that a radial seal that has a rotating shaft to seal on is going to be a different design than a hydraulic shaft seal of the same dimensions. The hydraulic shaft seals have a plunging shaft action, not a rotating fixed shaft. The sealing requirements seem to me as if they could require different seal lip designs.

I also browsed a Timken oil seal of this size:
https://cad.timken.com/item/seals/oil-s ... r2ls32-s-1
https://www.bdiexpress.com/us/en/Sealin ... p/21942240
although as I said, a double lipped radial seal may have too much stiction for this application, so it may be best to go with a seal lip design intended for push/pull hydraulic shafts like what Teknik offers as genuine Showa replacements, or perhaps what RaceTech also sells for these forks.


I have 3 of the PivotWorks kits for the 98 forks, I'll have to see if they include a seal like this.

-------------------


The Maier 596740 (black), 696741 (white), and 59674-30 (carbon fiber) 2000-2007 Suzuki DRZ400E & 2000-2022 DRZ400S Fork / Disc Covers (guards) for the externally-identical-appearing 49mm Showa open chamber conventional forks appear to be perhaps an exact fit for the RM 49mm Conventional Twin Chamber Showas from close comparison of photos, non-brake leg will be longer than the guard of course but the brake side looks to be an exact fit if using DRZ400 fork boots and fork boot clamps. The fork boot clamps attach to the lowers well below the seal area, which is clever and unusual, and in my mind appears to have been done to allow any water and sediment that finds it's way into the fork boot gaiter to find it's way to the bottom and well out of harm's way on the fork oil seal/dust seal area where it could cause damage. This has the unfortunate side effect of completely covering the outside of the fork legs with the Maier guard, DRZ fork boot clamp, and DRZ fork boot, but will protect them very nicely. The optional stock RM for guards were rubberized plastic and did not have a disc guard, and only the non-brake side is available OEM still, and even finding these optional OEM parts used from dismantlers as a set is nearly impossible (I've only seen non-brake side '96 model lower guards on any used forks, and I've been browsing these things on ebay for over a year).

https://maierusa.com/collections/maier- ... 4838018256


Showa 49mm open chamber conventional DRZ400 fork boots/lower mounts/clamps (2/ea.):
HOLDER,BOOT: 5120329F00
BOOT: 5157129F00019
BAND,BOOT UPR: 5157529F00 
(*upper boot clamp band is a thin metal hose clamp band, lower is simply just a black nylon zip tie)




Also noted that a lot of items showing in US distributor stock listed as unavailable, show up on European and other international distributors' sites as in stock, even CMSNL.com showing 1 left and 1 right complete 1998 fork leg damper assembly available - that's unrealistic at $2,650 USD for a complete brand new stock 24 year old (NOS) fork, but very surprising to say the least. OEM prices on the chrome upper/inner tubes and aluminum lower/outer tubes are pretty high though, but good to know 66% of them are still available new. Getting the tubes re-chromed from a service that does hard chroming or modern alternatives (the EPA has cracked down on chroming so much that most places don't do industrial hard chrome in small batches anymore, only for industrial/commercial hydraulic shafts generally).
Also, CMSNL shows multiple market region models for at least 2 of the 3 years, which have different parts, but what I have noted in part number referencing is that some model years simply used parts from the prior model year, likely to use up stock to make way for the next year's new improved updates/designs. Comparing to Partzilla will verify which of the two part numbers is actually for the US model year, and which is not. I found the CMSNL listing for US market was in fact not the correct model year, whereas the international market models was. At any rate, you need to ID the parts properly based on info contained here in order to determine if you have T, V, or W model years. Many sites list two model year letter codes under one numerical model year, even though the letter code directly translates to numerical model year. Interchange listings on sites used by eBay dismantler sellers will often get interchanges incorrect due to this numerical year showing model year letter codes for 2 or even 5 different years, giving you the option to select different letter code model year parts fiches that do not actually correspond with the numerical year selected.


-----------------------------------------------------------------------------------
Last edited by Chuck78 on 07:27 pm Mar 23 2023, edited 6 times 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
'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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Chuck78
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Re: Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by Chuck78 »

SPRING INFO:

(stock RM125 = .40kg, stock RM250 = .42kg)

***NOTE - I've read on the post linked a few post below this, from Thumper talk about 97 RM125/250 woods valving, that Negative Noel I believe it was stated that the springs race tech lists for the '98 forks will technically fit but are larger diameter and rub slightly on the outside diameter, and I did notice this one gathering all of the specifications that they were larger diameter by just a hair***


*'96 RM fork springs:
--Race Tech FRSP 4351## (## = 40 = .40kg, etc .42/.44/.46/.48/.50/.52/.54kg avail.),
43.2mm o.d. x 508mm free length, 312mm min.travel ***FRSP 4351 springs require special spacers.
--Eibach 974 (pre '07 KTM open cartridge 125t-450)
43.2mm o.d. x 508mm free length
--Eibach 980
43.2mm o.d. x 518mm free length
-OEM KTM WP:
2004-2005 KTM 200 EXC = .38kg
2006-2007 & 2010-2011 KTM 200 XC-W .38kg
2003 KTM 200 EXC = .40kg
2012-2016 KTM 200 XC-W .41kg

*'97 RM fork springs:
--Race Tech FRSP 4345## (## = 38 = .38kg, etc .40/.41/.43kg avail.),
43.2mm o.d. x 449mm free length, 312mm min.travel
--Eibach 977
43.0mm OD x 450mm Free Length
--Cannon Racecraft (may be slightly too long?)
# 43457 43.0mm o.d. x 457 mm free length, available in .36kg/.40kg/.42kg/.44kg/.46kg/.48kg/.50kg/.52kg/.54kg...up to .70kg (even rates)
(fits: "2008-2009/10"(??) KTM 200 XC {.38kg stock springs}

 
*'98 RM fork springs:
--Race Tech FRSP 4347## (## = 36 = .36kg, etc .41/.43/.43kg avail.),
43.2mm o.d. x 471mm free length, 311mm min.travel
******Eibach 983*****
42.2mm(?) o.d. x 471mm Free Length (via Race Tech)
available in .37kg / .39kg / .41kg / .43kg / .45kg/mm rates.
https://www.teknikmotorsport.com/983-Ei ... 42-2-x-471
These are the best to run as they are the same diameter as stock
(43.2mm fits but rubs a bit more than desirable,
'98 chrome tubes are apparently 0.50mm thicker walled tubing vs '97)

--Cannon Racecraft 43457
43.0mm o.d. x 457mm free length (preload spacers needed to make up the difference in length)
--Cannon Racecraft 43472
43.1mm o.d. x 472mm free length
--Cannon Racecraft potential lowering springs:
# 43457 43.0mm o.d. x 457 mm free length, available in .36kg/.40kg/.42kg/.44kg/.46kg/.48kg/.50kg/.52kg/.54kg...up to .70kg (even rates)
(fits: "2008-2009/10"(??) KTM 200 XC {.38kg stock springs}

Spring catalogs:
https://www.cannonracecraft.com/wp-cont ... atalog.pdf
https://racetech.com/download/FRSP-RTForkSpringsWeb.xls

Use 5wt suspension oil or 0w20w Mobil 1. The 0w20 Mobil 1 is very slick I have used it and like it a lot. 10wt is too heavy for the inner chamber, but you might get away with it in the outer chamber.
(-osobad on KDXRider.net)

Recommended oil level 405cc - 425cc, 5wt, recommended for spring preload 4mm (97-98)

*Note - spring spacer goes on the bottom
* Dual-Chamber Pressure Springs are there to prevent cavitation. They affect overall plushness on braking and square edge bumps. RT Pressure Springs fit both Showa and KYB.
2610 Series Pressure Springs (Race Tech says these fit '96, '97, & '98)
FRPS 261010 (26.2 x 102mm) - 1.0 kg/mm (160lb rider)
FRPS 261014 (26.2 x 102mm) - 1.4 kg/mm (200lb rider)
FRPS 261018 (26.2 x 102mm) - 1.8 kg/mm (240lb rider)
FRPS 261022 (26.2 x 102mm) - 2.2 kg/mm (280lb rider)
Cannon Racecraft Inner Chamber Springs for Showa:
Variable Rates: 1.2-2.2, 1.4-2.4, 1.8-2.8

Stock Twin-Chamber Pressure Spring Rate 1996 model - ?
Stock Twin-Chamber Pressure Spring Rate 1997 model - ?
Stock Twin-Chamber Pressure Spring Rate 1998 model - 2.74



*1996 parts:
Recommended oil level 420cc - 450cc based on desired bottoming resistance, 5wt, recommended fork spring preload 4mm
Inner Fork Bushings (pair) FMBI 49201 P $39.99 (OEM shows NLA except CMSNL.com, but aftermarket bushing kits are all over eBay)
Outer Fork Bushings (pair) FMBO 49152 P ($N/A,xx) (PivotWorks and other eBay kits have these included, OEM NLA also)
Fork Seals (pair) FSOS 49 P $21.98
Dust Seals (pair)FSDS 49 P $29.99
Damping Rod Bushings (each) SMSB 1010 $9.99
Damping Rod Bolt Copper Washer or O-ring (each) HMWC 1015 $4.99
Twin-Chamber Replacement Parts
Damping Rod Shaft Seal (each) FSTC CS1016 $13.99
Reservoir Rod Shaft Seal (each) FSTC RS1020 $10.99
Reservoir Piston External O-ring (each) HMOR 3528 $2.99
Reservoir Piston External Sliding Bushing (each) FSTC BI341001 $24.99
Reservoir Piston External Sliding Bushing #2 (each) FSTC BI341001 $24.99
Tools:
 Fork Shaft OD Holding Tool TFSH 10 $64.99
 Fork Cartridge OD Holding Tool (holds cartridge tube on OD for disassembly) TFSH 20 $64.99


*1997 parts: 
Recommended oil level 405cc - 425cc based on desired bottoming resistance, 5wt, recommended fork spring preload 4mm
Damping Rod Repair or Strengthening Nut FSRK 121002 $16.99
Inner Fork Bushings (pair) FMBI 49201 P $39.99 (OEM shows NLA except CMSNL.com, but aftermarket bushing kits are all over eBay)
Outer Fork Bushings (pair) FMBO 49152 P ($N/A.xx) (PivotWorks and other eBay kits have these included, OEM NLA also)
Fork Seals (pair) FSOS 49 P $21.98
Dust Seals (pair) FSDS 49 P $29.99
Damping Rod Bushings (each) SMSB 1210 $9.99
Damping Rod Bolt Copper Washer or O-ring (each) HMWC 1015 $4.99
Twin-Chamber Replacement Parts:
Damping Rod Shaft Seal (each) FSTC CS1217 $11.99
Reservoir Rod Shaft Seal (each) FSTC RS1020 $10.99
Reservoir Piston External O-ring (each) HMOR 3528 $2.99
Reservoir Piston External Sliding Bushing (each) FSTC BI341001 $24.99
Reservoir Piston External Sliding Bushing #2 (each) FSTC BI341001 $24.99
Optional repair kit repair nut for commonly stripped 6mm compression valve shafts FMRK 06 $29.99
Tools:
Fork Shaft OD Holding Tool TFSH 10 $64.99
 
*1998 parts:
https://racetech.com/ProductSearch/12/Suzuki/RM125/1998
Recommended oil level 405cc - 425cc based on desired bottoming resistance, 5wt, recommended fork spring preload 4mm
Inner Fork Bushings (pair) FMBI 49251 P $39.98
Outer Fork Bushings (pair) FMBO 491515 P $49.98
Fork Seals (pair) FSOS 49 P $21.98
Dust Seals (pair) FSDS 49 P $29.99
Damping Rod Bushings (each) SMSB 1010 $9.99
Damping Rod Bolt Copper Washer or O-ring (each) HMWC 1015 $4.99
Optional repair kit repair nut for commonly stripped 6mm compression valve shafts FMRK 06 $29.99
Twin-Chamber Replacement Parts
Damping Rod Shaft Seal (each) FSTC CS1016 $13.99
Reservoir Rod Shaft Seal (each) FSTC RS1020 $10.99
Reservoir Piston External O-ring (each) HMOR 3528 $2.99
Reservoir Piston External Sliding Bushing (each) FSTC BI341001 $24.99
Reservoir Piston External Sliding Bushing #2 (each) FSTC BI341001 $24.99
Tools:
Fork Shaft OD Holding Tool TFSH 10 $64.99

More parts:
https://www.teknikmotorsport.com/compli ... 98/#susPer


SKF Dual Compound seals and wipers highly recommended for lower friction, price is per side (1 kit = 1 oil seal + 1 wiper seal = 2 kits required per bike
Oil Seal: 49mm inner diameter x 60.6mm outer diameter x 6.0mm height
Dust Wiper: 49mm inner diameter x 60.3mm outer diameter x 10mm height
SKF # DUAL-49S
Last edited by Chuck78 on 12:15 am Feb 06 2024, edited 5 times 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
'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
User avatar
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Re: Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by Chuck78 »

Here is a year by year parts breakdown comparison of the 3 model years of these forks. Despite appearing almost identical externally, internally they are very different year by year as far as compatible parts swap ability, and have virtually no internal parts which can interchange with the nearly identical appearing open chamber 49mm versions on the DRZ400.
I do wonder if the lower outer tubes from the DRZ400 would accept the 97-98 RM internals and chrome stanchion tubes however. There are Chinese replacements for the outer tube portions above the axle lug to repair those forks which suffered a catastrophic amount of the dreaded 7000-series aluminum corrosion.

Also to be noted - when looking up parts fiches for these and many other model parts, DO NOT strictly go by the year listed, as many fiches will list a 1-year-only part across several model years' parts fiches. The proper way is to reference the MODEL YEAR LETTER CODE for the fork parts you are searching for. Every manufacturer has their own letter code for each model year. for Suzuki, W = 1998 m.y., V = 1997 m.y., T = 1996 m.y. (coincidentally also represents 1980 m.y. as well, they do recycle the alphabet after up to 26 years go by, but this should not cause confusion due to the drastic differences across that many years)

RM125 vs RM250 parts *should* all be identical for each model year aside from the tuning parts - valving assemblies and spring rates.



DAMPER ASSEMBLY,FRONT FORK RH ('98/W)
product number: 5110336E50
Hurry: only 1 left! € 1328.50

DAMPER ASSEMBLY, FRONT FORK LH ('98/W)
product number: 5110436E50
Hurry: only 1 left! € 1328.50



1 TUBE, OUTER RH
51130-36E00 ('96/T) € 656.00
51130-36E20 ('97/V) Unavailable (*swappable for '98)
51130-36E40 ('98/W) € 594.50 

2 TUBE, OUTER LH
51140-36E00 ('96/T) € 484.00
51140-36E20 ('97/V) Unavailable (*swappable for '98)
51140-36E40 ('98/W) € 441.00

3 TUBE, INNER
51110-36E00 ('96/T) Unavailable
51110-36E20 ('97/V) € 451.50
51110-36E40 ('98/W) € 345.50

4 BUSH, SLIDE
51121-36E00 ('96/T) € 16.50
51121-36E00 ('97/V) € 16.50 
51121-36E40 ('98/W) $30.39

5 PIECE, OIL LOCK
51195-36E00 ('96/T) € 43.50
51195-36E30 ('97/V) € 51.50
51195-36E50 ('98/W) Unavailable

6 PLATE, END
51205-36E00 ('96/T) Unavailable
51205-36E20 ('97/V) Unavailable
51205-36E00 ('98/W) Unavailable

7 O RING
51117-27C40 ('96/T) $4.89
51117-27C40 ('97/V) $4.89
51117-27C40 ('98/W) $4.89

8 BOLT, CENTER (top fork cap)
51170-28E30 ('96/T) € 138.00
51170-36E20 ('97/V) $166.52
51170-36E40 ('98/W) $168.67

9 GASKET (crush washer, omitted on 97/V & 98/W models) 51148-14D00 ('96/T) € 5.50
00 (crush washer omitted on 97/V & 98/W models)
00 (crush washer omitted on 97/V & 98/W models)
 
10 O RING 51177-28E30 ('96/T) € 3.50
9 O RING 51177-36E20 ('97/V) $3.79
9 O RING 51177-28E30 ('98/W) € 3.50

11 ROD, DAMPER 51190-36E00 ('96/T) € 459.50
10 ROD, DAMPER 51190-36E30 ('97/V) € 639.00
10 ROD, DAMPER 51190-36E50 ('98/W) € 462.50

12 TANK, SUB 51198-36E00 ('96/T) € 116.00
11 TANK, SUB 51198-36E20 ('97/V) Unavailable
11 TANK, SUB 51198-36E40 ('98/W) Unavailable

13 O RING 51174-43D00 ('96/T) $3.43
12 O RING 51174-29F00 ('97/V) $4.58
12 O RING 51174-29F00 ('98/W) $4.58

14 BOLT, FORK 51351-36E00 ('96/T) € 242.50
13 BOLT, FORK 51351-36E30 ('97/V) € 226.50
13 BOLT, FORK 51351-36E50 ('98/W) € 256.50

xx
xx
20 O RING, UPPER #2 ('98/W model only, omitted '96/T-'97/V) 51117-29EA0 $4.51

15 O RING, UPPER 51117-36E00 ('96/T) $5.45
14 O RING, UPPER 51117-36E00 ('97/V) $5.45
14 O RING, UPPER 51117-36E00 ('98/W) $5.45
 
16 BUSH, FORK BOLT SLIDE 51123-28E30 ('96/T) $11.35
15 BUSH, FORK BOLT SLIDE 51123-28E30 ('97/V) $11.35
15 BUSH, FORK BOLT SLIDE 51123-36E40 ('98/W) Unavailable****** (eBay alert)

17 O RING, CENTER 51174-28E30 ('96/T) € 4.50
16 O RING, CENTER 51174-36E20 ('97/V) € 4.50
16 O RING, CENTER 51174-36E40 ('98/W) $3.92


18 O RING _(lower)_ 51175-03B30 ('96/T) $4.30
17 O RING, LOWER 51175-36E20 ('97/V) $3.67
17 O RING, LOWER 51175-36E20 ('98/W) $3.67

19 BOLT, PLUG 51357-28E30 ('96/T) $11.31
18 BOLT, PLUG 51357-28E30 ('97/V) $11.31
18 BOLT, PLUG 51357-28E30 ('98/W) $11.31

20 O RING, PLUG 51358-28E30 ('96/T) $3.54
19 O RING, PLUG 51358-28E30 ('97/V) $3.54
19 O RING, PLUG 51358-28E30 ('98/W) $3.54

21 COLLAR, SPRING 51197-36E00 ('96/T) € 34.50 (*same location & type of part as SPRING, STOPPER)
20 SPRING, STOPPER 51355-36E20 ('97/V) € 16.00
21 SPRING, STOPPER 51355-36E20 ('98/W) € 16.00

xx (omitted on 96/T models)
21 RING, STOPPER 51354-36E20 ('97/V) € 3.50
22 RING, STOPPER 51354-36E20 ('98/W) € 3.50

22 JOINT, SPRING (omitted on 97/V & 98/W models) 51192-36E00 ('96/T) $8.08
xx (omitted on 97/V & 98/W models)
xx (omitted on 97/V & 98/W models)


23 SPRING, FRONT (K=0.40) 51171-36E00 ('96/T) € 67.00
22 SPRING, FRONT (K=0.40) 51171-37E30 ('97/V) Unavailable
23 SPRING, FRONT (K=0.40) 51171-36E50 ('98/W) € 60.00

24 COLLAR, SPRING 51176-36E00 ('96/T) € 120.00
23 COLLAR, SPRING 51176-36E20 ('97/V) € 111.50
24 COLLAR, SPRING 51176-36E40 ('98/W) € 119.00

25 SEAL, DUST 51173-36E00 ('96/T) $30.41
24 SEAL, DUST 51173-36E00 ('97/V) $30.41
25 SEAL, DUST 51173-36E00 ('98/W) $30.41

26 RING, STOPPER | Includes Item(s) 27 - 31(?) 51156-36E00 ('96/T) $5.99
25 RING, STOPPER | Includes Item(s) 26 - 30(?) 51156-36E00 ('97/V) $5.99
26 RING, STOPPER | Includes Item(s) ## - ##(?) 51156-36E00 ('98/W) $5.99
 
27 SEAL, OIL 51153-36E00 ('96/T) $29.43
26 SEAL, OIL 51153-36E00 ('97/V) $29.43
27 SEAL, OIL 51153-36E00 ('98/W) $29.43

28 SPACER, SEAL 51158-36E00 ('96/T) $6.66
27 SPACER, SEAL 51158-36E00 ('97/V) $6.66
28 SPACER, SEAL 51158-36E00 ('98/W) $6.66


29 BUSH, GUIDE 51167-36E00 ('96/T) € 20.50
28 BUSH, GUIDE 51167-36E00 ('97/V) € 20.50
29 BUSH, GUIDE 51167-36E40 ('98/W) $25.29

30 ROD, PUSH 51191-28E30 ('96/T) $15.84
29 ROD, PUSH 51191-36E20 ('97/V) $68.62
30 ROD, PUSH 51191-36E20 ('98/W) $68.62

31 BOLT 51321-27C40 ('96/T) $4.57
30 BOLT 51321-27C40 ('97/V) $4.57
31 BOLT 51321-27C40 ('98/W) $4.57

32 GUIDE, FRONT PROTECTOR RH 51211-36E00 ('96/T) Unavailable
31 GUIDE, FRONT PROTECTOR RH 51211-36E00 ('97/V) Unavailable
32 GUIDE, FRONT PROTECTOR RH 51211-36E00 ('98/W) Unavailable

32 GUIDE, FRONT PROTECTOR LH 51221-36E00 ('96/T) Unavailable
31 GUIDE, FRONT PROTECTOR LH 51221-36E00 ('97/V) Unavailable
32 GUIDE, FRONT PROTECTOR LH 51221-36E00 ('98/W) Unavailable

33 BOLT,______ 01547-06207 ('96/T) $1.88
32 BOLT ,______01547-06207 ('97/V) $1.88
33 BOLT, GUIDE 01547-06207 ('98/W) $1.88

34 PROTECTOR, OUTER TUBE RH (YELLOW) | OPT 51551-36E00-25Y ('96/T) Unavailable
33 PROTECTOR, OUTER TUBE RH (YELLOW) | OPT 51551-36E10-25Y ('97/V) Unavailable
34 PROTECTOR, OUTER TUBE RH (GRAY) | OPT 51551-36E10-1KY ('98/W) € 43.00


37 PROTECTOR, OUTER TUBE RH{LH???} (YELLOW) | OPT 51551-36E10-25Y ('96/T) Unavailable
34 PROTECTOR, OUTER TUBE LH (YELLOW) | OPT 51552-36E10-25Y ('97/V) Unavailable
xx PROTECTOR, OUTER TUBE LH (GRAY) | OPT 51552-36E10-1KY ('98/W) Unavailable 


35 WASHER, FORK PROTECTOR 09169-06053 ('96/T) $1.03
xx
xx

36 BOLT, FORK PROTECTOR 01547-0612B ('96/T) $1.14
xx
xx

39 SPRING, FRONT (K=0.38)(SOFT) | OPT 51171-36E10 ('96/T) Unavailable
36 SPRING, FRONT (SOFT,K=0.38) | OPT 51171-36E40 ('98/W) € 180.50
35 SPRING, FRONT (K=0.42)(HARD) | OPT 51171-37E20 ('97/V) € 45.00



1996 RM125T:

Image

1997 RM125V:

Image

1998 RM125W:

Image
Last edited by Chuck78 on 09:21 pm Nov 20 2022, edited 4 times in total.
'97 KDX220R - purple/green! - KLX forks, Lectron, FMF, Tubliss
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Re: Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by kdxdazz »

Great write up, very detailed, just out of interest do you have any photos of the drz400 convential fork shim stacks and valving, I'm the guy that posted the 43mm showa fork conversion, are the showa 43mm and showa 49mm basically the same fork or do they have completely different internals, I like you do not like USD forks, I did buy a set of drz400 forks to fit but changed my mind due to being difficult to source light springs, I run a 4.2kg rear spring on both my kdx's and they are perfect for my 140 pound weight
1999 KDX220SR (KDX220-B5)
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Re: Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by Chuck78 »

kdxdazz wrote: 08:12 pm Nov 20 2022 Great write up, very detailed, just out of interest do you have any photos of the drz400 convential fork shim stacks and valving, I'm the guy that posted the 43mm showa fork conversion, are the showa 43mm and showa 49mm basically the same fork or do they have completely different internals, I like you do not like USD forks, I did buy a set of drz400 forks to fit but changed my mind due to being difficult to source light springs, I run a 4.2kg rear spring on both my kdx's and they are perfect for my 140 pound weight

Are the 43mm Showas off of a newer DR-Z 250? Race Tech does not list all DRZ250 years, they do list the old school damper rod fork versions, but I believe perhaps around 2007+ the DRZ250 got Showa 43mm conventional cartridge forks as an upgrade to the ancient basic damping rod fixed orifice setup prior.

No I don't have any, but Thumper Talk forum is an awesome source of in-depth valving info for Showa Twin Chamber forks in general as well as the Open Chamber DRZ400 forks. I do have a link for that. Someone on KDXRider.net had posted a link and used the DRZ400 Thumper Talk 49mm open chamber valving discussion as a basis for their 49mm RM twin chamber Showa valving setup, even though the forks are COMPLETELY DIFFERENT internally... piston diameter will affect the shim stack specs a bit, that should definitely be considered.
Due to having so much money wrapped up into buying 4+ sets of these 98 RM forks in an attempt to just get 1 or 2 nice condition sets built out of the parts, I will now likely be opting to revalve them myself and learn more about valving forks (with many rides + teardowns to revalve most likely, lol...) as opposed to having ZR1 or WER or JD Suspension revalve them for me once the best pro way... so maybe I'll have some further insights into the valving by next spring.

Here ya go:
https://www.thumpertalk.com/forums/topi ... ns/page/8/

Also, if you still have those DR-Z 400 forks and plan to use them, refer to my two links for Race Tech and Cannon-Racecraft fork springs above, you most certainly can find some lighter .38kg or even .36kg springs for the DR-Z 400 forks especially if you know the outer diameters compatible with the fork, and the approximate fork spring free length (there is more wiggle room here with shorter springs able to be shimmed with more preload spacers).
Last edited by Chuck78 on 09:09 pm Nov 20 2022, edited 1 time in total.
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Re: Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by Chuck78 »

This guy gearheadE30 is AWESOME for making these very informative videos on these 96-98 RM 49mm conventional forks.



Showa 49mm Twin Chamber conventional RM125/250 forks, differences between '96 & '97 (& some '98 commentary):





Teardown and technical assembly/disassembly info:

Part 1:

Part 2:

Part 3:



And this is regarding the later inverted Showa Twin Chamber rebuild procedures, but this still has some helpful info on these:

https://dirtrider.net/how-to-rebuild-sh ... 9mm-forks/

Last edited by Chuck78 on 02:52 pm Nov 25 2023, edited 1 time in total.
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Re: Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by Chuck78 »

Okay.... now as far as the triple clamp swapping goes to get these to fit onto a KDX frame.

The RM frame's head tubes and steering stems are shorter than that of the KDX/KLX frames and 1991 & older KX frames.

The classic option of doing a stem swap works here as well, and as typical, the press-fit diameter of the KDX's lower stem area is several thousandths of an inch smaller, and is a loose slip fit which most people resolve by having a machinist knurl the stem area until the outside diameter of the knurling is an effective press fit diameter, and then use retaining compound to even better secure the stem once pressed in. Retaining compound is also referred to as the type of loctite labeled for "permanent bonding of cylindrical parts."
A very thin spacer will then be required to make the Suzuki's upper triple clamp fit the smaller diameter KDX stem as is typical for most popular KDX fork swaps.


It should be noted that the RM and DRZ400 lower triples have a very tall raised step directly under the bearing seat area, and for these things to fit a KDX frame properly and not sacrifice fork travel range (i.e. interference between the lower outer tubes' dust seals vs impacting the bottom of the triple clamp on suspension bottoming), while the stem is pressed out, it's critical to mill off or turn down most of that raised step on the Suzuki triple clamp, and if using the KDX steering stem, to cut the stem down so that the diameter of the lower bearing press-fit area extends down appropriately - as the bearing will not press down into the triple clamp to stem press-fit area as this is slightly larger than the bearing press fit area.
Here are some photos borrowed from elsewhere in this forum regarding these RM Showa swaps:



drawing image from TheRadBaron:

Image

(I don't plan to use the RM stem, and therefore am not foreseeing the need to recess the stem up further into the lower triple clamp for my methods as TheRadBaron here has done, I want a taller amount of stem to lower triple contact for strength, although most street bikes still run about the same amount of press fit height that TheRadBaron ended up with after figuring out how to utilize the stock RM stem with no other pieces needed to be sourced or custom machine such as upper triple stem spacer sleeve etc).

Here are two photos from forum member Gotanubike which show a similar stem mod in order to use the stock KDX stem machined to fit + an upper triple clamp collar/sleeve/bushing/spacer as with most KDX stem swaps into other forks:

Image

Image

Image


( I should note that due to the required travel range vs available height of the chrome tubes on the 97-98 forks being nearly maxed out, I plan to mill off even more of the raised aluminum area below the lower stem bearing on the RM triples vs what this other KDXRider.net member has done above, leaving just enough so that there may be 1mm of space from the KDX frame's head tube to the triple clamp areas, and perhaps take 0.75mm off the bottoms of the lower triple clamping area just as extra insurance if I feel that I'm still close to the dust seal being able to bottom on the underside of the triple @ the chrome tube clamping areas)
Last edited by Chuck78 on 12:00 pm Dec 06 2022, edited 5 times in total.
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Re: Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by Chuck78 »

The stock steering stem on the RM forks is aluminum, as are most motocross bikes' stems since 1990-ish, in order to save every bit of weight in every way possible... This is a nice bonus but the RM stem is too short to run in the taller KDX frame's head tube.
One member did make this work by machining that raised lower bearing seat area off the lower triple as pictured above, and boring out the lower triple's stem hole from the underside, in order to recess the stem up higher to get the correct amount of stick-out height. This leaves less than desired press fit height in my opinion.

From my vintage street bike fork swap researching, I knew that Suzuki used this same style aluminum stem on a variety of different bikes, Hayabusas, GSXR's, V-Stroms, etc... Well... The GSXR stem I have fits a Suzuki GS400/550/750/1000/1100 frame and is a similar height to the aluminum RM stems... running some 43mm conventional forks as a swap onto a Suzuki GS, we discovered that the early non-ABS model V-Strom DL1000 had 43mm conventional forks and an identical looking aluminum steering stem that was slightly taller than the GSXR stems and needed some shims to fit the Suzuki GS frames.

Well guess what... $2.98 + shipping & I now have in my hands a non ABS model (older) V-Strom DL1000 43mm street bike 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 ONTO A KDX FRAME, appearing to be the exact length needed for the KDX frame! This should be a direct swap to press out the RM/DRZ steering stem, machine the step down to almost nothing on the lower triple bearing seat area, and press in the DL1000 VStrom stem... no knurling needed, no upper triple clamp spacer sleeve on the KDX stem to fit the RM triple, and you can keep the fancy lightweight aluminum stem feature of these swaps!
Showa49mmRM125_steering_stem_swap_DL1000-VStrom.jpg
Showa49mmRM125_steering_stem_swap_DL1000-VStrom.jpg (93.71 KiB) Viewed 5699 times
The earlier aluminum-stem version DL1000 V-Strom lower triples seem prevalent and cheap on ebay, so I think this is definitely the best answer to swap a Suzuki RM triple clamp set onto a KDX, by getting a DL1000 lower triple as a donor for the stem only, to transplant into the RM lower triple clamp.


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...


Also noted, the DR-Z 400 49mm conventional forks' triple clamps can be directly swapped, but the DRZ triples have less offset than the RM triples. Less offset increases steering trail specifications for more high speed stability at the expense of low speed maneuverability (slower stable steering vs quick turning ability), and the DRZ400 49mm triples having less offset will also reduce the maximum lock to lock steering ability, not a good thing for a bike oriented to tight woods riding.
Another thing to note - don't fret when you notice the KDX triple clamps have considerably more offset to them than the RM and DRZ400 49mm conventional forks. This is a package deal of sorts, and is accommodated for by design. The massive 49mm conventional fork legs are significantly larger diameter on the inners and outers than the stock KDX forks, and also use a more standardized and burly 20mm diameter axle vs the KDX's 15mm front axle. The larger diameter tubes and larger diameter axles on the 49mm conventionals puts the front axle's center point obviously a noticeable bit further forward when hugging the fork tubes vs the KDX's conventional forks' axle centerline vs fork tube centerline. The total fork leg leading axle lug axle position + fork tube lower's radius is nearly identical in total leading offset of the 95-06 KDX forks and triples. within 0.5mm from my approximate measuring, so the steering characteristics should be very similar between the two.


If running the Suzuki steering stems with the 30mm i.d. bearings top and bottom, these are the steering stem bearings you'll need (All Balls part #'s):
Bottom bearing kit, part# 99-3519-5, 30x55x17
Top bearing kit, part# 99-3540-5, 30x47x12

Stock KDX / KLX / KX500 bearing & frame area = 15mm tall, therefore you'll need to make up 3mm worth of spacer with a 30mm slip fit i.d. I believe AllBalls sells various thick spacer washers.
I plan to use the V-Strom DL1000 steering stem, which instead of one spanner nut on top of the bearing/bearing seal, uses 2 thinner spanner nuts with a toothed washer in between them, in conjunction with a keyed slot machined into the steering stem for the toothed washer to lock into. Instead of putting the two spanner nuts directly against each other with the washer in between, I plan to have one nut under the dust seal, and depending on the thickness, I hope to have enough room to fit the keyed/toothed washer UNDER the dust seal while still keeping this dust shield right up against the frame without too tight of a tight fit and also without a large gap, and lock the second thin spanner nut down from above. This will make bearing adjustment a bit more time consuming, but also helps reduce the triple clamp's stack height overall, as to not infringe on the fork travel range. The KDX frame's head tube is notably taller than the Suzuki's, and therefore a longer portion of the chrome tubes' length gets eaten up by the triple clamps' necessary spacing. Milling the raised portion down off of the bottom triple's bearing seat area, as well as keeping the upper triple as close to the frame as possible (with only having 1 of these thinner spannner nuts sitting above the frame's head tube, will both allow a longer portion of the chrome tubes to be available for the fork travel range. With right-side-up forks, internally lowering to avoid this type of contact (dust seal to triple clamp on bottoming out) does not work, as that relationship does not change when lowering them.
Luckily as with nearly all forks, the "12.2-inch" advertised travel on these is not the real world travel, but the total amount when going from fully topped out (which never really happens even with the lightest rebound + very heavy tires/tubes + hang time in the air when jumping). With these forks hanging in the air, no wheel or brake weight, pulling the lowers downward and letting them rest, judging from the "witness marks" (wear marks & patterns in the dried-up oil/dirt residue on chrome), these forks when lightly topped out have an 11.6" travel range without yanking on the top-out springs while measuring. With my mods to the triple and the DL1000 steering stem, I should be in the clear on available travel range just by a smidge, even without the thinner DL1000 steering stem spanner nut vs a 3mm thick spacer and the thicker RM steering nut,


******This is also a noteworthy mention for those running the DRZ400 49mm conventionals, that they may instead want to track down a 96-98 RM125 / RM250 triple clamp set for their KDX woods bike.
Last edited by Chuck78 on 11:42 am Dec 06 2022, edited 3 times in total.
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2001+ RM125/250 47mm inverted Showa Twin Chamber swap info

Post by Chuck78 »

One other discovery that I made, the 2001-2008 RM125 Showa 47mm Twin Chamber inverted/upside-down forks *may* also potentially fit directly into Honda CRF250X etc triple clamps without a stem swap, for swapping onto the KDX. CRF250X, R, & CRF450X/R also use Showa 47mm 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 a 2001-2008 RM125 47mm Showa twin chamber fork may potentially work in these triple clamps, if it all fits right, could perhaps be one of the most ultimate inverted fork swap setups if fitment did all work out, so that you wouldn't have to do a stem swap even.

Although as a comparison just for reference, looking at the 2005+ Yamaha YZ's KYB S.S.S. forks, even with the same diameter chrome tubes, the aluminum outers / uppers had different upper clamping diameters for the upper triple clamp area only, 2-stroke versus 4-stroke, for some strange reason. If the 47mm RM versus CRF twin chamber forks have the same clamping diameters and the slightly taller stem was the right height, 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 softer for woods and springing the main spring for your weight, or if you are 165lbs-180lbs 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 (still far less prone to cavitation on high speed riding than an open chamber woods fork).
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Re: Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by Chuck78 »

Since I have had absolute $#!+ luck with actually buying (online) a set of these RM Showa 49mm conventional forks with what I consider to be good usable chrome finishes with no significant defects in the chrome seal travel areas, and I suspect everyone else may also be subject to this same poor luck with 24-26+ year old forks, here is a link to the only company which I have found which was a viable option to ship the bare chrome upper/inner 49mm tubes off to for *PROPER* hydraulic shaft re-chroming:

EC Chrome & Grinding - motorcycle fork tube and shock shaft re-chroming



"Our standard price to repair/rechrome fork tubes is $225.00 per tube plus 15% hazardous waste fee ($33.75) – total of $258.75 each. Shipping and tax are not included in base price. Payment would need to be made prior to the finished parts being returned.

If you decide to move forward, please send us ONLY the fork tubes along with your contact information inside the box.

Thank you,

Debbie S. - Office Manager
Electronic Chrome & Grinding Co., Inc.
9128 Dice Rd
Santa Fe Springs, CA 90670
562-946-6671 Phone"



Also, due to my misfortune and struggle to find a set that is both described by the 5 different sellers as having "perfect usable chrome in the seal travel areas with no noticeable defects" AND a pair that actually arrives and passes this same inspection request with my own eyes, this is a very good reason why the 96-98 RM 49mm Showa Twin Chamber conventional "best woods forks of all time" may be time to step back from that title for practicality sake for the majority of us.

I say this because the 2000-2022+ DRZ400 49mm Showa conventional forks are much newer and have had less years of use and abuse, and also come from the factory with accordion pleat boots over the entire chrome seal travel range of the upper/inner fork tubes, therefore they had been fully protected their entire lives from stone chip and crash damage in the seal travel areas, vs the RM forks which only had a roost guard type front plastic protector built in to the number plates, which protruded down and shielded only the fronts of the fork tubes from any abrasions or stone hits...
The closed chamber / twin chamber design is more advanced and very nice for being able to handle a wider variety of terrain and riding styles, but also is not necessary vs open chamber forks for just doing slower technical woods riding which the KDX was designed for, particularly the KDX220R models. BUT... If you are lucky enough to find a good set of 96-98 49mm conventionals, or don't mind shelling out the cash to get a set of chrome tubes re-chromed, then this thread has perhaps the most info you'll find anywhere on these RM conventionals!

Just keep in mind on the DRZ400 49mm open chamber versions, that the first 2 years or so of the S model forks 2000-2001 I believe, are not cartridge forks internally, but rather 49mm forks with old school fixed orifice damper rods. Very basic and not at all an upgrade for anything other than 1992 and older KDX's which also used the same fixed orifice damping technology... still for those 92 and older models, it's a lot of effort involved to swap them for no damping upgrades.
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Re: Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by Chuck78 »

Here's the Thumper Talk extensive discussion on how to make Showa closed chamber fork valving plush for woods riding:

https://www.thumpertalk.com/forums/topi ... ds-riding/
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Re: Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by SS109 »

Wow, super detailed and informative. Thanks for sharing all your hard work with everyone here on the forum
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Re: Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by kdxdazz »

Had to order a second coffee at my local coffee shop to get through all this info🙂 it appears from your description that the 43mm and 49mm showas are completely different internally, the 43mm showas has an most identical shim stack to the stock kdx forks except they use 12 shims and they are not a true shim stack anyway as the don't flex, they only separate, my 43mm showas are from an xr400, 0.32kg fork springs are what I need to suit my weight and they weren't available for the drz400 forks from memory, my idea for triple clamps was to use the kdx250 triple clamps then machine up some bushes to take up the slack from the inverted forks, would need 1mm thick bushes from memory, I think using the skf seals is an important point, my xr400 forks have terrible stiction from using the all ball seals and my recently rebuilt rear shock would barely return without the spring thanks to the horrible all balls seal head stiction, skf seals feel so soft and supple compared to all balls, shitty cheap crappy product in my opinion
1999 KDX220SR (KDX220-B5)
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Chuck78
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Re: Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by Chuck78 »

There's a ton of info on revalving twin chamber forks on Thumper Talk, some on Vital MX on these forks also. Thumper Talk really seems to be where the most technically minded DIY mechanics/riders hang out.

Here's a link on what some guys did to '97 RM125 and '97 RM250 forks to get them ready for Eastern woods racing, and the Negative Noel guy that I quoted above in a few places in my initial compilation of notes, he came out and posted a revised version of their stack for the '98 since it has a 10 mm damping rod same as '96, versus the '97 having the 12 mm damping rod. Only a very slight change to compensate for the different volume displaced.
It sounds like those guys were pretty happy with the valving. Noel said it was more plush than his open chamber forks on fast choppy trail riding.
SKF low friction seals or SKF dual compound low friction seals ($$$ & sold per side, buy 2 sets of oil/dust seals) again sound like they are highly recommended for any twin chamber/ closed chamber fork such as these.
Also I should reiterate that with any of these forks even the KYB SSS, you need to pull them completely apart every 100 hours or once a season and replace the inner chamber seals, as all the damping oil is contained inside the inner chamber, and when those seals fail, you lose your damping as well as lubrication on the piston.

I'll cut and paste and summarize a lot of this here so it's all in one place:
https://www.thumpertalk.com/forums/topi ... 250-forks/

One thing that was never mentioned in there was the internal chamber pressure springs. RaceTech lists no spec for the 96 and 97, but instead says to call them. Their general guidelines chart says that a 160lbs woods rider like myself wants their lightest ICS spring, the 1.0kg. Browsing '01-'08 RM125 Showa Twin Chamber 47mm inverted forks, ICS for those years are 1.15, 1.4, 1.45 kg. The CRF250X Showa 47U TC forks, a woods bike, use 1.5 kg inner chamber pressure springs. The CRF250R or CR250R uses a bit firmer around 1.9kg from what I read.
Of the 96-98 Showa 49C TC's, Race Tech only list '98 @ 2.74kg inner chamber spring, which seems a bit on the harsh side, and I have a hard time believing is the correct information based on people's reports of these forks being pretty compliant even stock, although these definitely still benefit from a woods revalving though from what more serious woods riders say.
The '99 RM125 49mm inverted Showa Twin Chambers list 2.74kg ICS as well, and '00 losts 1.01kg. A lot of people complained that the 99 forks were not a good ride whatsoever. So the 2.74 makes more sense on that one to me.
I'm just struggling believing that spec is correct for the 98 also. I would check it myself but I haven't had much luck with online spring rate calculators being accurate, too many variables of materials. I'll probably buy some soft ones and compare them in person to judge.

Here's another less in depth post, 96 RM250. this guy wasn't happy with the Motocross valving for Eastern woods racing, and use the demo version of ReStackor to model different shim stack mods, and came up with this, although he did not post after testing them as it was winter time:
https://www.thumpertalk.com/forums/topi ... ds-stacks/
Last edited by Chuck78 on 09:30 pm Apr 26 2023, edited 5 times 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
'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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Chuck78
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Re: Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by Chuck78 »

There's a lot of debate when the closed chamber/ twin chamber forks' inner chamber springs are discussed, some people say the only way to make a twin chamber fork plush is to run a softer inner chamber spring, which will then allow it to cavitate a bit more easily, which one of the main points of designing them as a twin chamber is to reduce cavitation. Others say that the inner chamber springs help with cavitation the most on a woods bike when the bike isnear the top of the stroke, and that riding a motocross track gives much slower suspension movements albeit a lot heavier/deeper hits, as they're on a smooth track and landing jumps at great speed to distribute the landing force across a distance, versus rapid suspension movements blasting through rough woods sections, where a firmer inner chamber spring would be needed according to this opinion.

Luckily on the 98's that I've got a collection of here, they have the quick change base compression cartridges, like all of the newer '99+ forks, so you can pull out the base valve and inner chamber spring without even without taking the fork off off the bike or draining it...

I may try a couple different versions of these as they are quite affordable compared to the main springs, & may buy the Race Tech 1.0 kg versions, and try the Canon Racecraft 1.2-2.2 progressive rate versions.

People that seem to be more in the know definitely argue that you should spring keep the firmer inner chamber springs, then spring the bike properly with the correct main spring rates for the fork, and figure in that these (quoting/paraphrasing discussion on the CRF450R forks' 1.9kg ICS springs) inner chamber springs will add .01kg/mm to the overall total spring rate of the fork springs when considering overall main spring selection, and then valve them slightly more plush on both the base and mid. Apparently the rebound on these is pretty good stock.

This I'll have to do some more reading on, as race tech pretty much says that the 1.0 kg are what I need for woods riding. I do like it extra plush. I blast through a lot of nasty rock sections in second and third gear, sections that are absolutely bone jarring on my wife's 2007 KTM 200 XCW according to MY experiences. She says her bike is the best and mine sucks and there's nothing wrong with hers lol...(except that it's an absolute missile that she rides rather conservatively and always fouls plugs on... Which also might be why she says the suspension is perfect! When I get on it I don't take it easy whatsoever, pinned every moment possible! And the fork is harsh...)

I think I might have just saved myself from having to hire suspension shops to revalve the forks at least. Running an '01-06 RM 125 shock however, I might be a bit in the dark on. I'll have to find a manual for the shock rebuild. I don't believe it requires much in the way of specialty tools other than soft jaws (I use wood blocks and holesaws/drill bits and space the 2 blocks apart a very small amount before drilling). I've got the nitrogen charging tool covered already. RaceTech probably lists the tools needed for these things, I'll just have to figure it out...
Last edited by Chuck78 on 09:34 pm Apr 26 2023, 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
'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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Chuck78
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Re: Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by Chuck78 »

Service manual suspension section download for a '98:

'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
User avatar
Chuck78
Supporting Member II
Supporting Member II
Posts: 609
Joined: 06:20 pm Nov 30 2016
Country: USA
Location: Columbus, OH

Re: Showa Twin Chamber 49mm conventional forks 96 97 98 RM125/250 + inverted Showa TC & RM shocks, & DRZ400 49mm forks

Post by Chuck78 »

I spent a lot of time in the past week reading up on Showa valving for woods, I'll post some more tips that I've cut and pasted.
I think I had a few tabs bookmarked for revalving the Showa shocks as well. I'll need to look up the tools needed to do a proper disassembly of these, but I think that, armed with some first-hand experience of people more knowledgeable than myself about valving, I might be able to get this valved pretty good on my own... It will be a good learning experience regardless.
I'll cut and paste and dump a bunch more info here in the next few weeks when I have free time, after riding a season is over here December 11th (All the State Forest & National Forest OHV/APV trails in Ohio close Dec. 12th thru April 1st).
My '99 KDX220R is sitting in the basement with 4 other bikes all awaiting rebuilds/restorations, the KDX might be the top priority out of bikes that aren't my wife's which obviously by default get pushed ahead of anything of mine 😂😭
Off to begin reassembling her '88 BMW R100GS right now, before I get in trouble for not already being out there working on it!
'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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