Fork Spring size and length

[Bailey28]

I just picked up astock '05 200 with 10 minutes on the clock. I have been reading that the forks are the first thing to make stiffer, so I wanted to try that before heading out to the woods and track.

I am having difficulty finding the longer XR springs in the .42-.43 range I want, as it seems that Race tech and Eibach are selling the shorter 472mm length spring for every model with the 43mm forks, XR, KDX, etc. Race tech even lists the XR400 replacement springs as the shorterFRSP 3647 series. I would be disappointed if I owned an XR and ordered a set and found they were 60mm shorter than my stock ones!

I weigh 180 lbs without gear and ride 50% woods and 50% track, mostly vet friendly tracks, never race or jump more than a 30 foot table. I am coming off of a 2004 YZ250 smoker that is simply more bike than I can handle or get used to. On a track, I am semi aggressive in whoops and berms, but I'm not a huge jumper. I ride in Florida on everything from sand to clay hard pack. I have been searching here for the past few days and it seems that everyone is recommending the .40 spring weight for woods, but I wanted a little heavier rate for the track.

Short of going to thumpertalk and asking for some used XR .400 springs or paying $73.85 each for XR650L .440 springs from RonAyers, what else can I look for? I did notice that one post had early 1990's KX250 springs as a suggestion, but their size is 38.2mm diameter by 512mm in length. I guess I need to pull off the fork cap and measure the inside diameter to see...

I would email Jeff Fredette, but after reading that the XR springs make the front end much better, I don't want to tie him up only to have him recommend the shorter ones anyway. :blah: Any input would be appreciated.

 

[glad2ride]

Why do you want longer springs?

Eibach 996 springs are longer than OEM.

No need to get excited about the RT springs being shorter than OEM for a Honda XR400R. Most any spring will need a spacer cut to a custom length, and 472mm is long enough for XR or KDX travel.

How long are XR650L springs?

The KX fork springs you mentioned are probably too large a diameter to fit in your KDX forks.

ANY fork spring of the correct rate will make the forks better. The springs he offers for sale are 470mm - 475mm in length.

 

[Bailey28]

Thanks for the advice! I looked at the white brothers catalog and found that the 996 eibachs are longer than stock at 512mm. The more spring the better as I wanted max plushness and still be able to absord a big hit.

 

[glad2ride]

Uhhhhhhhhh, ANY spring will only compress so much, which is 290mm at the claimed travel. If your forks were ten feet tall and you had a 3 meter-ish spring, it still would only compress 290mm. More spring = more weight, though only a little.

Do you know how long XR650L springs are??

 

[Red_Chili]

FWIW, I too weigh 180-185 without gear. I recently put some used XR400 .39 springs in, removed two shims from the valve bodies, SAE5 fork oil at 100mm, ~20mm preload, and find the fork action to be really, really nice. The first thing I noticed was a bonus feeling of confidence, then I realized why. The stock front knobbie, nothing to write home about, stuck like glue. This was at an MX track tooling around, then dinking on piles of dirt, dropoffs, all sorts of obstacles, not terribly aggressive but just all-round stuff.

 

[glad2ride]

Hi. Are you saying you have OEM Honda brand springs or aftermarket springs that will fit in a Honda XR400R? I have read that they are .38 or .40 is why I ask. Thanks.

 

[canyncarvr]

re: 'The more spring the better..'

Suited me!

re: 'ANY spring will only compress so much..'

Uhhhhh.....yep.


re: 'If your forks were ten feet tall and you had a 3 meter-ish spring, it still would only compress 290mm'

Yep again. But that's not the direction he (Bailey) wants to go. He wants to change from a 10' fork/3 meter spring to a 10' fork/6 meter spring.

You're welcome to argue otherwise and welcome to run any spring you like. Heck..put in a 24" steel spacer and a 12" long spring if you like. It appears senseless to me to take something that is supposed to house a spring (a fork tube) and fill it full of steel tubing spacer.

Besides, the proof of the pudding being in the eating and all...my OEM fork suspension improved greatly with a change from OEM length to a .38 XR/longer spring.

Nope. Not everyone that has tried it likes it. They're welcome to not. I don't ride their bike. ;)

Don't bother asking Mr. Fredette. Anything I've read concerning his choice in spring is to run the 470mm with a long spacer.

The spring diameters are listed on the RaceTech site (for one place anyway). Knowing the diameter you're after, you should be able to come up with most any length you want...who cares what make/model/year it's listed as fitting.

Example: The longer XR spring in the KDX fork will give you little room if you're interested in running a small preload spacer. But, you can get the same diameter spring for a Yamaha that is 10mm shorter than the XR spring. There 'ya go!

If nothing else, call someone like Mr. Wilkey (MX-Tech), tell them you want (as an example) a 46mm diameter spring that is 515mm long with a .42 rate.

Yeah...I wouldn't be happy with a shorter spring than what I started with, either.

Not where I got mine...but I've heard of a number of KDXers getting their XR springs (used) from a thumpertalker. Usually pretty darn cheap, too.

Good luck!!


BTW...
My OEM KDX springs were around 470mm in length. My XR springs were 520mm or so.

 

[glad2ride]

LOTS of conventional forked bikes use a spacer to take up the gap. When the spring eventually sags, and it will, there would be nothing to take up the space otherwise. No matter how long or short the spring is, measure the gaps between the active coils and that is as far as it will compress.

If it makes the OP happy, then go for it, but don't stress too much about it.

I know you have KX forks on yours now, so I will leave you with your past memories of longer springs. :-)

 

[saveaux]

For the type of riding you do I would suggest scouring EvilBay for some sort of new front forks. Whether they are KX forks or CR forks thats up to you. Theres plenty of information on these forums to properly do the swap. I personally ordered brand new XR400 springs at $37 dollars a piece. After shipping I ended up spending around $90. The results that I got were.....well.....decent. You will still have mad fork flex, horrible handlebar flex (thanks rubber mounts) and the undesireable underhand that the stock KDX forks have.

You can find fork sets on EvilBay all day long for $100-$400. Often times they are around $150. Although I am praising different forks I haven't done the swap, YET. On that note I'm not sure of exactly what you will need. I think this is a basic outline of how it works: most KX forks can use your entire brake setup, you will need your KDX stem pressed out of your triple clamps and installed onto the KX triple clamps, I believe your KDX wheel will not work so you will need a KX wheel also. If your at all intrested in doing this (which I HEAVILY recommend, especially since you do light MX) do some research and I think you will be happy with what you find.

 

[MY KDX 220 R]

Strange no one has remembered that Jeff Fredette has all that you need, KDX experience included.
Why would you go for any thing less, check out his web site. You will go faster and have the plushest ride your buddies on other "woods" bikes will envy?????????????
I have his fork springs and pipe gard, check out a modified or full "experimental" carb.
Have fun.

 

[Bailey28]

Thanks again for the input.

When the springs get to the house, I will be in the garage for a while setting up the front like this:

.43kg/mm springs from Eibach, their 996 series at 512mm free legnth

5mm preload

oil at 135 mm from the top, tubes compressed springs out

the first two shims removed from the valve stack

mix 5w and 10w oil for a 7.5w blend Belray


I hope to get a plush initial travel for small stuff, and have the heavy springs soak up the bigger hits. I don't jump very high, maybe 5 feet off the ground at the most. All of the tracks I ride are easy vet and I don't push aggressively or have anything to prove. I know that I can just about bottom the stock forks in my front yard now.

If the rebound is too fast, I will run a 10w or a 10w 15w blend and go softer on the compression to keep the plushness. I hope to keep the initial plushness also by running less preload. I run the forks at the top of the triple clamps, as came stock for stability.

 

[glad2ride]

Sounds good, but keep in mind that oil weight affects compression and rebound. Just keep messing with it until you like it.