Rear Shock questions and Ideas

[Chopperpilot]

I have a 2001 KDX 200. Last summer (short here in Alaska), I got much better at off road riding techniques and hill climbs. I've already grafted a set of 93' KX250 forks to the KDX and will either gold valve them this winter and/or try putting on a 2003 YZ250 front end that I got a crossover bearing to fit the KDX frame. I'm pretty decent at rebuilding and shim stacking for suspension (I first learned this on mountain bike forks and shocks).
Anyway, onto my question. I've read a lot from Chuck78 and SS109 on fitting Showa suspension pieces to the KDX (notably the rear shock). I have 2 dirt bikes, the KDX and a 1996 KLX 650R (I rebuilt the forks on this bike with gold valves). I have a good feel for what I want out of a fork, but am looking this winter to spruce up the rear end of both these bikes. Both bikes have essentially the same shock on them, which everyone agrees is 'a pretty decent shock'. Having never tore down or done any maintenance to the rear of these bikes, I'm sure just a standard rebuild/grease will show significant improvement, but what's the fun in that? So I'm going to either install gold valves in the shocks, or replace the 'pretty decent shock' with Showa 50mm versions (probably also gold valved or shim swapped at least). I'm curious from people here who have modified the rear end, will a Showa (rebuilt and valved nice) be that much of an improvement over a Gold Valved KDX shock? I think the improvement I'm looking for, or hoping to get, is better stability/tracking when climbing hills with semi large rocks (basketball and bigger) on them. Something that will 'float' over these things with a little less commotion than I currently have. I've heard the Gold Valves (and recommended shimming) should do this exact thing....... will a Showa do it that much better?

[KDXGarage]

I can't remember. What have you already done to the shock?

What is your weight in full riding gear and the current shock spring's rate?

[Chopperpilot]

I've done nothing to the rear end at all. I assume I have the stock 5kg spring on the KDX. In full gear I'm about 200lbs.

[KDXGarage]

I think you will need the 5.2. It will ride better after proper linkage / bearing maintenance and fresh oil and nitrogen. Don't place too much faith in your current worn out setup to make decisions off of.

[Chopperpilot]

Noted and thanks! I ordered 2 of the Gold valve kits for the KYB 44mm shocks (the KLX650r essentially has the same shock). I'll just rebuild and gold valve both of them. I have two Showa 50 mm shocks I got cheap off ebay (1 DRZ400 and 1 RM125) and I'll tear them apart at the same time to see if I notice anything worth the extra expense in fitting to either bike. I'll also check to see if either will easily fit to either bike. I suppose I can also actually check sag and race sag on both prior to disassembly and see about springs for either if necessary.

[KDXGarage]

Good luck with it all. Congratulations on getting the Gold Valve kits. It will take a lot of guessing out and should get you in very good shape.

[Chuck78]

Regarding the 44mm KYB vs 50mm Showa, critics really praise the 50mm KYB on the 2024 Beta 200RR Race Edition, and talk bad about the standard 200RR & older model years of the 200RR Race Edition - citing the 46mm(?) Sachs shock doesn't have enough fluid capacity or shim stack diameter/surface area to really be competitive... It's all relative though, as a KDX guy that lives his KDX200H with Race Tech Gold Valves in the stock suspension (44mm KYB shock) also was saying this same thing that the Sachs 46mm shock was too small versus the new Beta model 50mm KYB shock...

[Chopperpilot]

Ok, stripped a lot of the bike down tonight. I guess I'm lucky! the rear linkage looks to just need a cleaning and repacking, everything still actually moves! The rear shock has some oil on the shaft, so it's good I was going to overhaul it anyway. So right now I have 3 ebay shocks, a DRZ, a 2005 RM, and a 2006 YZ (I was hoping to get the titanium spring, but accidentally made an offer on the wrong one!). I also wanted to see if maybe the YZ 46mm body could be adapted to the KDX shaft easily for something better than the 44mm KDX shock body. Well comparing the two, the reservoir on the YZ comes down way too far to be of use.
Now, comparing the DRZ shock to the KDX..... it's only a touch longer, and if I redrill the clevis from the 2005 RM and build the DRZ shock with that, I think it'll be very very close to KDX length. I'm definitely going to experiment with that.
I was happy that all the linkage bolts came out easily, and were clean with a little bit of lube on them. Even the swingarm bolt came out easily.
I just need to find a service/rebuilt kit for the 44mm KYB shock now.

[KDXGarage]

Technical Touch has the parts. They are sky high now!

[billie_morini]

Of course, the parts price is sky high! Just bought 2 performance tires for my supercharged MINI Cooper. The price for 2 of these tires was enough to purchase 4 tires the last time around.

[Chuck78]

Now, comparing the DRZ shock to the KDX..... it's only a touch longer, and if I redrill the clevis from the 2005 RM and build the DRZ shock with that, I think it'll be very very close to KDX length. I'm definitely going to experiment with that.

Cool, that sounds like a pretty excellent combo from the parts you have!

Based on your other thread, I'm thinking some of those Yamaha triples that have the longer steering stem (is the 4mm shorter stem going to still work for the KDX frame? Seems you thought the 2003 steering stem would be too long but it ended up working?), if there is a Yamaha WR250 fork that fits in that or if the WR250 steering stems are good for the KDX frames with those special size 12mm tall conversion bearings, then this is really perhaps the ultimate setup for a KDX swap, hands down!

I suspect that some of the KYB 46mm 1994-ish-2005 KX125 shocks may also work out very well to fit the KDX to match a Yamaha WR250 fork's ride height...and the WR250 off-road models will already have decent woods valving for trail use...

Similarly, I'm thinking the '96-'97 RM125 Showa 46mm shocks could also be the best Showa shocks to swap, but if my crankcase clearancing works out well, I'm absolutely running my 50mm "FrankenShowa" shock build and it's titanium spring that I picked up...

By the way the Yamaha OEM Titanium springs were not of the best reputation, with people cracking them due to alloy content issues. Diverse Spring lightweight Silicon-Chrome springs are the best bet, as the good RCS (Renton Coil Spring) Titanium shock springs are $499 new...

[Chopperpilot]

I read a lot that seemed to point any factory YZ titanium springs cracking was due to these plastic clips that are on each end to prevent it making contact with itself. Apparently they fall out mildly regularly and if you just ignore it, you can break the titanium spring.

[Chopperpilot]

So, after getting the YZ front forks squared away and pulling the top end off to see what it needed (sending it off for a replate and might as well do the big bore while there) I started on the rear shocks. Right now I just have the KDX shock dismounted and I squeezed a 2003 DRZ shock in it's place to 'see'. Today I disassembled the two Showa shocks (2003 DRZ and 2005? RM 125) to see about swapping up parts in them. The 2005 RM shock has the longer clevis, but looks to be able to be drilled to a shorter overall length than the DRZ setup. The DRZ has a shorter body though. Well here is the DRZ body with the RM shaft (larger 18mm shaft). The red circle is a mark I made where I believe the clevis can be drilled for the KDX knuckle without having to clearance anything. A slight bit more could be had with some beveling/sanding.

IMG_1688.jpg (618.45 KiB) Viewed 7008 times

IMG_1687.jpg (2.84 MiB) Viewed 7008 times

Anyway the DRZ body with the RM shaft, if the RM clevis is drilled to a shorter overall length looks to be like it could be within 5mm of the KDX length.
I also had gotten a YZ shock off ebay with the intent to see if the 46mm body could be used with the KDX shaft, it cannot, the reservoir is way to long on it. I then wanted to see if perhaps the spring was a slightly smaller diameter but would fit on the Showa, and reduce the interference with the engine case at top out, this will not work either. The spring outer diameter appears to maybe be a couple mm smaller than a showa spring, but the ID prevents it from being able to slip over the showa bottom spring retainer piece that stays on the shaft. So now I will just see if maybe the HS compression adjuster can be put onto the KDX shock, maybe?
Having the Showa shock be the same length as the KDX shock will definitely ease up on the clearance required of the engine case as the knuckle moves further away at shorter lengths.
My next move will be to take apart the KDX shock and compare total travel (minus bump stops) between the KDX and the Showa DRZ/RM combo. One interesting thing is that the RM shaft is noticeably longer than the DRZ shaft. The RM seal head had a top out spring that limits the free extended length of it and the DRZ seal head did not have this. I'll also use my drill press and drill the clevis out for the shorter length. I figure I can tap the other side just like the KDX setup so that there's no need to put a nut on the other side of the clevis.

[KDXGarage]

Please be aware of "inside the body" length of travel. I am seeing the rear tire go through the fender and eat the toolbag.

Install them without springs and check travel.

[Chuck78]

I wouldn't offset drill that clevis too much at all, it will generate more side load the shaft, which is not a good thing, but is workable to a certain extent, it will just place a little bit of added where on the shock body, piston band, and seal head. A slight bit should be fine but I would still consider clearancing the crankcase rear portion for the majority of the clearance.

The guy that has all of the race team KX450 parts for sale was heading out of town and doesn't seem to have had the time to measure the shock for me, but I think that 2024 KX450 shock could be quite workable and clear the crankcase on the KDX has it has a tall lower spring seat that completely encompasses the bump stop, and at bottom out, the shock body will be inserted deeply into this lower spring seat. I need to find out the length though as it advertises 2023 and 2024 as being 475 mm although they were completely different and I had read that the 2024 shocks were made shorter for fuel pump placement reasons and other reasons with the bike design.
These are very expensive forks & shocks though, most people are absolutely not going to want to spend the money for 1-year-old race team take off parts from current models when rebuilding their KDX.

I'm very curious to see how the longer RM clevis from the 2005 and up or KX250F 2006 and up would clear especially when combined with that DRZ400 body.

[Chopperpilot]

Oh, I'm not going to offset drill (I didn't say that though). I just made that mark when I was sliding the knuckle into the clevis. I wanted to accurately eyeball the center of the hole in the knuckle and make a vertical reference point on the clevis for where the centered hole would be.
Possibly a touch higher with clearancing the clevis and knuckle some.

[Chuck78]

If you are putting a longer shaft in the shorter body, I personally would look into some of the extended piggyback reservoir and caps so that you can have a little bit more volume of nitrogen in there so that the reservoir can take up the extra amount of fluid being displaced from a longer shaft and shorter body. Race check sells them, then there's a generic that's very similar, and then MX Tech or someone sell some that are a burnt bronze type brownish color, goldish brown I don't know how to describe it. There are at least 10 different configurations of the caps depending on what bike. I found a chart showing all of them but I can't remember which website it was on

[Chuck78]

I've gotten a good deal eBay seller offer, so I snatched up a '96 RM125 46mm KYB shock as well...purchasd yesterday on eBay, arriving TOMORROW!
Allegedly these are 444mm length according to the Teknik Motorsports website, which is right around the absolute maximum usable length for the stock KDX frame shock mount location and stock rocker linkage, while being 46mm piston size vs the others we've been working @ a modern size of 50mm, with that are best off with some filing/grinding to clearance the back of the crankcase in a thick and non-significant area, these '96-'97 46mm Showas look to not likely need any clearancing, and may fit length-wise with maybe a 2mm lowering spacer internally at most, or none at all! I'd bet a similar era '96-'98 or '99-'02 KYB from a KX125 would be a fairly similar fitment. KYB didn't move up to 50mm shocks until several years later.
The 50mm is the golden standard in these modern times, but I feel a 46mm will not leave an average woods rider much of anything to complain about at all... and the compression adjuster assembly looks to be the same still, so a 2002+ DRZ or 2001+ RM etc would probably be able to swap the dual compression adjuster in place of the single adjuster, but really the Lainer Suspension '08+ KX250F Showa adjuster looks to fit the '98 RM just fine, and the '96 adjuster looks identical to the '98. I may try to get a 2006-2008 YZ125 OEM Yamaha Titanium 4.8kg spring and open up the lower spring seat inside diameter (they taper inwards) to run a budget used titanium spring on this 46mm shock as well...
The 50mm FrankenShowa is still definitely going onto my '99 KDX220 since that one's not in riding condition now and engine and whole bike due for a complete overhaul, so that frame's shock mount will get chopped up to move the upper mount rearward 6mm and upwards 14mm-16mm... The swingarm pivot/engine mount combo bolt area of the crankcase still needs clearanced/shaved for topped out spring clearance on the 50mm Showas, but the engine case is 10mm thick around the first 25mm left and right, and the center section where the clearancing is needed is 7mm thick roughly. This shouldn't be any issue. I can JB Weld the inside of the case there when I have them split if there's any question of strength, but Kawasaki hollowed it out from the inside out in the center area of the cases, so I highly doubt this will be any issue.

The '97 RM125 is also a 46mm shock, but listed as being 447mm length from Teknik (vs 444mm for the '96 version), and they do carry a different part number '96 vs '97, so that may perhaps be correct (their measurements are occasionally slightly erroneous, so I have found).

With that and KLX300 117mm pull rod links, the KDX will sit around a hair under 1" higher in the rear than stock, which is really about perfect for the KDX for riders 5'10" and taller, more ground clearance and more available travel.


I'm also pretty close to pulling the trigger on some 2022, 2023, or 2024 KX450X forks on ebay... I have a triple clamp set in the mail which I'm fairly confident will be very workable on the KDX frame with a conversion upper bearing size, and modifying the steering stops. So we now have CR/CRF, YZ250 2-stroke and *some* WR250, YZ450F, YZ250F triples, and 2019+ KX 4-stroke triples that are the right height for our KDX frames, and as of late have available 28mm and 30mm i.d. 47mm o.d. conversion bearings available! This is a big breakthrough...
I need to find a better set of lowers for my '97-ish KX500 forks (hoping to upgrade to a '99-'02 set of KYB 46mm lowers) and sell them as a KDX bolt-on package deal upgrade before I tell too many people about these new fork swap options! Steering stem swaps as I always say seem like a shame to downgrade to a hefty steel stem and machine shop knurling and bushing making just to get modern forks, these new options will allow use of the aluminum steering stems to keep things simple and save a lot of weight...
I was blown away that some fork swap UPGRADES to generally all LARGER diameter forks that are MORE RIGID, would drop 3, 4, even 4.5 lbs off the weight of the KDX! I'm still running the -1/2lbs weight savings 1998 RM125 forks on one of my two bikes though... RIght side up conventionals... I sure wish Showa would just remake a modern version of those Twin Chambers, or just a lightened up + mid-valve added version of the open chamber variant on the 2000-2024 DRZ400...