XR Spring rates for Conventional KDX Forks

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Indawoods
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XR Spring rates for Conventional KDX Forks

Post by Indawoods »

Xr600 93-00 : .41
Xr600 85-92 : .42
Xr650L 93-02: .44
Xr400 98-04 : .40
Xr400 96-97 : .38

It’s the 1996-97 0.38kg/mm XR400 springs that are interchangeable and commonly used in 1995 to 2005 KDX200/220s

The stock 1995 to 2005 KDX 200/220's springs are commonly used to replace the 1989 to 1992 KDX springs, they are a good fit and give much more support in these models.

The Stock KDX spring rate depends on the year of the KDX. The 89-92 KDX's had a .29 spring rate stock. The 95-04 KDX's have a .35 spring rate.





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2004 XR400 springs

Post by TopperHarley »

I picked up a set of springs out of a 2004 XR400 supposably rated at .40kg. will these work in my 02 or 05 220R? Or did I waste a whopping 5 bucks?
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Post by AZRickD »

What weights are those springs able to handle?

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Post by GhostRider »

I have explored the race tech site and have discovered that you can use DR springs in kdx's, just something you could possibly add to this list.
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Post by KDXsg »

Hi, what year and model of the DR fork spring should I look for? do I still need to ditch the long metal spacer and cut the PVC pipe for it? thanks for any advices.
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XR Spring rates for Conventional KDX Forks

Post by crs »

[Have searched but can't spot an answer to this...]
The stock 1995 to 2005 KDX 200/220's springs are commonly used to replace the 1989 to 1992 KDX springs, they are a good fit and give much more support in these models.
The springs in the 89-92 forks are 496mm as standard - and I think the springs in the 95-05 forks are about 480mm... If you do this swap, what about a preload spacer? (How long and where to put it?)

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Re: XR Spring rates for Conventional KDX Forks

Post by KDXGarage »

Modern preload is very little compared to 20 years ago. For example, Race Tech suggests 4mm instead of the 10mm that they used to suggest.

If you are going to use .35 Kg/mm rate springs with modern preload amounts, I hope you weigh 125-ish in gear. That is what they are good for (if that).

I want to say there is a thread on here with how to calculate spacer length to get the correct amount of preload. You may try searching for that.

This is not a full detail way, but...with top cap resting on top of spring, washers and spacer, hold inner fork tube, so outer tube is hanging in free weight...measure distance from top of inner fork tube up to the underneath edge of the fork cap. "Nowadays", 4mm is good.

Just know in your heart of hearts that using modern preload amounts on a spring that is from the "high preload / soft rate spring" theory time frame is going to feel too soft.

The massive stock spreload puts the spring further into compression to start with.

Someone/somewhere used to have a spreadsheet showing preload and spring length. One could see that a stiffer spring with little preload was initially softer than the massive preload and soft spring method.

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Re: XR Spring rates for Conventional KDX Forks

Post by crs »

Thanks for that - good info...

This is my actual situation... I've just got hold of a 99 KDX 220 SR and, after feeling how soft the front end is and checking Jeff Fredette's guide on the KDX (http://www.frpoffroad.com/aboutus.htm), I ordered some .38 springs to suit my weight (I'm 70kg - about 90kg with all riding gear). Got the springs and went to swap - only to find the bike's actually fitted with 89-92 forks. According to the Fredette guide, I want .35 springs (= the standard springs for the 95-05 forks) to suit my weight in the older forks...

So now I'm wondering what to do. The problem is made more awkward because I'm in Thailand, where most of these kind of bikes are scarce and sourcing new or used parts normally means ordering from the US. I could try the .38s (but sounds like they'll be too stiff) or I could sit and wait for some .35s to come from the US (or I could bite the bullet and go the way of KLX300 or KX500 forks). Maybe the .38s with a spacer giving less preload (like 4mm) might work OK? (The 89-92 forks were running about 10mm preload after checking). Anyways, thanks for the help. Cheers.
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Re: XR Spring rates for Conventional KDX Forks

Post by 6 Riders »

Freddett's spring guide said I needed .38s, I ended up w/.41s and they are about perfect. I wouldn't worry about being a little heavy from his guide. Use 7wt oil and oil height to smooth things out for your riding style. Give it a go, if it doesn't work for you, THEN you can source new springs or (even better) a fork swap.
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Re: XR Spring rates for Conventional KDX Forks

Post by crs »

Will try. Might get Race tech Emulators too... Cheers.
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XR Spring rates for Conventional KDX Forks

Post by crs »

Weird... My bike's a 220 SR and turns out it has fork outers that look like those on a H but they've been made to fit E internals. Anyone else seen this? Must have come from the factory like this.
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