43mm showa fork conversion done

Questions and comments about converting to beefier forks..
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kdxdazz
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43mm showa fork conversion done

Post by kdxdazz »

For those that were contemplating the xr400 fork conversion, here it is
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Re: 43mm showa fork conversion done

Post by Chuck78 »

Nice work, KDXazz! I was always curious about the XR400 and DR-Z 250 forks. I think the DR-Z forks are a different fork internally, but they are the same 43mm size and also made by Showa.
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Re: 43mm showa fork conversion done

Post by Chuck78 »

I hear you 100% on the constant leaking issues of upside-down forks, they blow seals at least once a season usually due to mud drying up on the chrome tubes, being so close to the ground, and some of the dust making it's way past the dust seal and into the oil seal, which packs in and eventually spaces the sealing surface out and causes gravity to leak out the fork oil since they're inverted...

Also, the chrome tubes are far more susceptible to rock damage on the slow technical trails, which will do your forks in... right side up conventionals will usually just get a little bit of damage to the exteriors cosmetically. Every once in a while you might bash one so hard that it gets dented, but also, you can run full wrap around fork protectors to prevent that so much... inverted forks only have the fronts of the chrome tubes protected. the back sides can still get the chrome gouged up and chipped. Once that happens, say goodbye to your fork seal rather quickly, and then all of your fork oil very very quickly following...

I like the 1998 RM125/250 conventional forks which are a little bit more complex twin chamber version of the 2000-2023 DRZ400E forks and 2004-ish through 2023 DRZ400S open chamber forks, 49mm diameter Showa conventional right side up forks on both. I'll be swapping both of my bikes eventually with those.
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Re: 43mm showa fork conversion done

Post by kdxdazz »

Thanks Chuck, manufacturers went the upside down route because they have a nice clean look despite they make no sense for enduro and sometimes you have to sell what the public wants, not what makes sense,
my bike handles amazing, so plush, I'll try to do a full video at some point on the rear shock rebuilding and valving, all the advice I got in the past to set it up for a lightweight was completely wrong but after a couple of years experience under my belt and lots of studying I was able to figure it out
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Re: 43mm showa fork conversion done

Post by bufftester »

It had nothing to do with the look of the bike, it's because it provides a more rigid front end connection at the steering stem. It wasn't for weight savings or unsprung weight issues, strictly rigidity, which directly translates to more precise steering. Keep in mind this came out of the motocross world and not Enduro/trail-riding, but in dirt bikes everything starts at the motocross line and trickles down. One of the main reasons the Suzuki 49mm conventionals is such a sought after item is the incresased rigidity they provide, while still keeping the sliders protected.
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Re: 43mm showa fork conversion done

Post by kdxdazz »

Rigidity for motorcross, in the 90's motorcross bikes had USD forks, enduro bikes had conventionals, to say looks played no part I think is incorrect, people associate conventionals with low tech and low performance, which they kind of are 30 years later, motorcross got all the attention in the 2000's and people want what people race, also ridgitity wasn't as critical In the 90's but as people became more over weight it does become more important, it's like horsepower, mostly useless for the average rider but on spec sheets would you buy the 30hp bike or the 40hp bike
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Re: 43mm showa fork conversion done

Post by Chuck78 »

@kdxazz please do share with us what you did to the rear shock valving setup.
I'm real curious about these forks now. They have been on my radar before but I explored other options instead.
Less underhang and more adjustability would be a very good thing.
I was contemplating using my stock KDX forks to swap onto my 1977 Suzuki PE250 2 stroke enduro, after shorting them internally about 1.25". I do recall contemplating swapping a DRZ250 fork onto them in the past as well, probably after reading of another KDX owner doing the same.
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Re: 43mm showa fork conversion done

Post by Chuck78 »

The 96-98 RM Showa 49mm Twin Chamber conventionals really seem to be the best all around for Woods riding so many ways, and it's a shame that the Japanese manufacturers got out of the serious woods bike game for the most part. If enduro racing was as big back then as it is now, those forks would probably still be in production, and we would still probably have a KDX and RMX 2-stroke offerings at the dealers if two stroke woods bikes were as popular back then as they are now for the past 8 years or more...
At least Yamaha is still keeping it real with the YZ250X and YZ125X woods bikes. I don't understand why they would not have just punched out the 125 to a 144 like all of the other small bore 150 class woods bikes these days though... Or added electric start and a real lighting stator.
Still crossing my fingers that we may see a KDX300R or whatever they might call it in the next model year or two! :supz:
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Re: 43mm showa fork conversion done

Post by SS109 »

Eh, the Japanese dropped the ball and now the players are Rieju, Sherco, Beta, TM, KTM and their rebranded names. They are the 2T market now.

Even Yamaha's offerings are not as good as any of them. My buddy has a 2018 YX250X. While it has been a solid and reliable bike it isn't without critique. It has only a 5sp transmission and the internal ratios are just odd, no e-start, came with substandard hardware, no ability for running a headlight, and, not a biggie to me but is considered mandatory by some, no hydraulic clutch. Yes, it is considerably cheaper than the others but, well, you get what you paid for which is less of a bike.
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Re: 43mm showa fork conversion done

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I'll try do a video sometime soon on the rear shock although not sure how to do it given the shock is already in the bike, the Xr400 forks I did enlarge the ports slightly on the valves, you could probably find my post about this somewhere and I think I took out 2 shims, I used belray 2.5W fork oil which is one of the lightest fork oils, I'm using 0.32kg forks springs from an early kdx which is perfect for my puny weight and set the front sag at 55mm my cutting a spacer to length, front fork sag seems seldom talked about but I've found it to be critical, the more sag the harsher it becomes due to increased fork angle
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Re: 43mm showa fork conversion done

Post by Chuck78 »

One other thing which I just stumbled upon again was mention of the last updated version DR350 forks (98-01, the gold lower tube Showa versions with almost no underhang), which are very similar to the DRZ250, DRZ400, XR400R, and RMX250 forks, in 43mm versions with .39kg springs. That would suit a 160lbs-ish rider give or take pretty well slid in a pair of KDX triples.
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Re: 43mm showa fork conversion done

Post by Chuck78 »

Just FYI... on 43mm Showa forks.
I really think these are an awesome upgrade over the stock forks that is a pretty simple bolt on, and I looked into this a little bit further after getting another tip off.

So all years XR400R & DR-Z 250 have nice fully externally adjustable 43mm gold leg Showas with the aluminum colored axle lugs and 17mm axles. The DRZ250 valving is a little bit non-standard, and RaceTech currently does not support those forks at all as they have never had any on their bench to see what fits.
Well... Turns out the last 3 years or so of DR350 also have very similar Showa 43 mm cartridge forks with gold lowers and aluminum axle lugs, 17mm axle, .39kg springs. The street model DR350 SE I believe also may have these, but I didn't check the spring rates. I believe this was 96-99 or 97-99. The SE is the street model so perhaps the valving is a little bit different, but no fork swap would be complete without also doing some custom valving or Race Tech Gold Valves and their custom shim stacks.
Then I later read even more about this that tipped me off to the fact that DR650 SE models 1996 or 1997 to PRESENT still run Showa 43mm forks!
EDIT - the '96+ DR650 are the same externally, but use very basic damper rod internals.
The XR400R Showas use Race Tech Gold Valves # FMGV 2001, whereas the DR350/DR350SE use FMGV 2040.


I was really excited to learn of this, as those forks are much nicer than our stock forks but will bolt right into the triples. More external adjustability, slightly lighter and weight, and a larger diameter axle that will help with getting rid of some of the flex that the stock front end suffers from if you push it hard.

I'd really go with DRZ400E 49mm open chamber conventional Showas or 96-98 RMX250 46mm open chamber conventional Showas if I had the time to do the machining to the triples and stem swap to fit, but these 43mm Showa options are fantastic to learn of.
I've got a pile of 98 RM125 49mm Twin Chamber conventional Showas that I'll be running, I don't really recommend these because one of the internal chamber seals is very specific to this fork 96 97 and 98, and is tougher to find, as well as bushings for the 96 and 97. Each year has its variances but they're all very closely related in design and function. All of the others discussed here are open chamber forks, and they all basically look the same besides some being larger diameter.
Excellent forks. I just wanted to add that about the DR350, and DR350SE forks also being the same family and a direct swap into our triples.
Last edited by Chuck78 on 06:32 am Jan 29 2024, edited 3 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: 43mm showa fork conversion done

Post by kdxdazz »

Chuck78 wrote: 09:07 pm Nov 20 2023 Just FYI... on 43mm Showa forks.
I really think these are an awesome upgrade over the stock forks that is a pretty simple bolt on, and I looked into this a little bit further after getting another tip off.

So all years XR400R & DR-Z 250 have nice fully externally adjustable 43mm gold leg Showas with the aluminum colored axle lugs and 17mm axles. The DRZ250 valving is a little bit non-standard, and RaceTech currently does not support those forks at all as they have never had any on their bench to see what fits.
Well... Turns out the last 3 years or so of DR350 also have very similar Showa 43 mm cartridge forks with gold lowers and aluminum axle lugs, 17mm axle, .39kg springs. The street model DR350 SE I believe also may have these, but I didn't check the spring rates. I believe this was 96-99 or 97-99.
Then I later read even more about this that tipped me off to the fact that DR650 SE models 1996 or 1997 to PRESENT still run these same forks! They have .41kg springs leave, according to race tech, all the years that I looked up. The SE is the street model so perhaps the valving is a little bit different, but no fork swap would be complete without also doing some custom valving or Race Tech Gold Valves and their custom shim stacks.

I was really excited to learn of this, as those forks are much nicer than our stock forks but will bolt right into the triples. More external adjustability, slightly lighter and weight, and a larger diameter axle that will help with getting rid of some of the flex that the stock front end suffers from if you push it hard.

I'd really go with DRZ400E 49mm open chamber conventional Showas or 96-98 RMX250 46mm open chamber conventional Showas if I had the time to do the machining to the triples and stem swap to fit, but these 43mm Showa options are fantastic to learn of.
I've got a pile of 98 RM125 49mm Twin Chamber conventional Showas that I'll be running, I don't really recommend these because one of the internal chamber seals is very specific to this fork 9697 and 98, and is tougher to find, as well as bushings for the 96 and 97. Each year has its variances but they're all very closely related in design and function. All of the others discussed here are open chamber forks, and they all basically look the same besides some being larger diameter.
Excellent forks. I just wanted to add that about the DR350, DR350 SE, and DR650SE forks also being the same family and a direct swap into our triples.
good write up, a couple of things that i learned when looking for forks, i looked at a couple of sets of drz350 forks and none on them were adjustable except for preload, not exactly sure which forks they are and the dr650 from memory is not adjustable also or maybe for compression only but all these examples are in australia,maybe you guys got different forks,
parts fiche shows the rmx forks to be near identical to the 43mm so i didn't see any reason to go with those although they do seem like a great option,
i was all set to do the drz400 swap until i learnt light springs are not available for the drz and at 49mm a little over kill for single track,i had the drz400 forks and the kdx250 triple clamps, my idea was to machine up some brass bushes to take up the slack in the kdx USD triple clamps
i also have a set of kdx220sr forks here, different valving system than the regular kdx but from what i know they are so much more plush
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Re: 43mm showa fork conversion done

Post by Chuck78 »

Cannon Racecraft I believe sells lighter springs for all of these forks mentioned, including the DRZ400E. They may even list that one in their applications. Some bikes you will find springs for via Cannnon Racecraft by browsing spring dimensions, if not otherwise listed by them. They seem to have a better selection than Race Tech.

My apologies if I jumped the gun on boasting about the DR350 and DR650 forks, perhaps they DO NOT have externally adjustable rebound as the XR400R forks do?
EDIT - the '96+ DR650SE forks are the same externally / visually, but use very basic damper rod internals.
The XR400R Showas use Race Tech Gold Valves # FMGV 2001 with .40kg springs, whereas the DR350/DR350SE use FMGV 2040 and .39kg springs.


I thought the RMX250 forks did have externally adjustable rebound, but perhaps I was mistaken. The 46mm diameter RMX250 forks are a definite good upgrade for the KDX, as the height is the same as the KDX, and they are already valved for woods stock, unlike nearly all MX forks.
The XR400R forks still then seem to be the best overall setup. I don't care for the stock valving in them as much as I do in the stock KLX300R forks (much better, but still could use some tweaking), but that's easily re-valveable.
Last edited by Chuck78 on 06:30 am Jan 29 2024, edited 1 time in total.
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'99 KDX220R project - '98/'01 RM125 suspension, Titanium hardware, Lectron Billetron Pro, Tubliss
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Re: 43mm showa fork conversion done

Post by kdxdazz »

yes the rmx forks are fully adjustable,i was meaning i think they are identical internally to the xr400 forks but not 100 percent sure about this, maybe the later model dr350 forks are fully adjustable but the ones i saw weren't . i still think the 43mm showa forks with some gold valves will be up there with the best options, the standard xr400 valving is the same as the standard kdx forks except 12 shims, i ported the vlave slightly and removed 4 shims
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Re: 43mm showa fork conversion done

Post by Chuck78 »

Good to know. Yes I believe that 96+ Showa 43mm forks, the ones with the gold 7000-series aluminum tubes with the aluminum colored lugs, are rebound adjustable as well as compression, but I should really check on that to be certain. '95 & older DR forks are definitely not, and are the original design from '88 or '90. 96+ DR650SE forks look identical on first glance, but are damper rod internals.
Last edited by Chuck78 on 06:40 am Jan 29 2024, 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
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'88 Suzuki Samurai TDI/Toyota swaps
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Re: 43mm showa fork conversion done

Post by Chuck78 »

EDIT - the '96+ DR650SE are the same visually on the external appearance, but use very basic damper rod internals.
The XR400R Showas use Race Tech Gold Valves # FMGV 2001, whereas the DR350/DR350SE use FMGV 2040.
'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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