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XR4 Front suspension/springs

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I've been severely disappointed with my 98 XR4 front suspension at the track so I decided to perform the shim stack mod.  After pulling the compression bolt, I count only 7 shims (stock shim count for 96 & 97) rather than the stock 12 shim count that a 98 is supposed to have.  So this tells me that someone has replaced the front forks.  Ok, so I pull the spring and see that it has an aftermarket Eibach spring that is stamped with 21/93  996.024.0.  I cannot find this spring anywhere on the internet but it really sounds like a 24 KG/MM spring rate.  I really hope not because I am 180 lbs and that is a much lower spring rate than stock on a bike that is already undersprung. 

 

So can anyone tell me what the specs of this spring is and what the 21/93 means?

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The way I understand Eibach codes is:

 

-21/93 is the week and year of manufacture of the spring

-996 is the spring series (36.7mm O/D, 510mm long)

-.024 is the spring rate in lbs/in; converts to .043kg/mm

 

I don't know what the final digit signifies.  It may be a version number, ie 0 is the original version, and any modified/updated version of the same specification spring may be given a 1 etc.

 

Re the shims:  measure the thickness of each of your 7 shims; they may be 7 of the original 12.  From memory, the 12 shim stack has all .004" shims and the 7 shim stack is 5 x .005" and 2 x .008".

 

Cheers,

Gary

Edited by RMXR

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.43 should be fine for 180lbs (if that is what they are). I would not go any heavier or you will not have enough rebound damping and you will get a front end that pushes in the corners.

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The way I understand Eibach codes is:

 

-21/93 is the week and year of manufacture of the spring

-996 is the spring series (36.7mm O/D, 510mm long)

-.024 is the spring rate in lbs/in; converts to .043kg/mm

 

I don't know what the final digit signifies.  It may be a version number, ie 0 is the original version, and any modified/updated version of the same specification spring may be given a 1 etc.

 

Re the shims:  measure the thickness of each of your 7 shims; they may be 7 of the original 12.  From memory, the 12 shim stack has all .004" shims and the 7 shim stack is 5 x .005" and 2 x .008".

 

Cheers,

Gary

 

 

 

I call Eibach and they didn't know what those springs were, "probably an item we used to carry but no one bought them so we discontinued them".  So thinking it was 24kg/mm, I just ordered the 47kg/mm.  Maybe I should stop the order before it ships.  I do have an OS Clarke tank though.

 

As far as the shims, there were 2 x .008" and 5 x .005", I removed the 2 x .008" shims from each valve.

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.43 should be fine for 180lbs (if that is what they are). I would not go any heavier or you will not have enough rebound damping and you will get a front end that pushes in the corners.

 

I tend to bottom out on most jumps...and my front end already pushes.  hopefully the shim stack mod will help the pushing but im really wondering about the springs now...

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Also forgot to mention, the "fork oil" I poured out was actually transmission fluid :facepalm:

Plenty of people swear by ATF.  It has about the same viscosity of Maxima or Bel-ray 10wt.  Though most people tend to use 5wt in their XR4s.

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I agree with Redpoint. ATF is a good fork oil, if you want that viscosity. But I find 5wt. better for being able to more closely fine tuning suspension compression and rebound. Each clicker setting doesn't have such a drastic effect with the thinner oil.

The shim stack mod will mostly effect hi speed fork action damping, think rocks and roots.

What front tire and pressure have you been running all this time, because tires are not all created equal when it comes to holding a line in corners and not pushing out, regardless of how the suspension is set up. Some tires just s*ck.

Then there's the fact that you're trying to ride track with a trail bike, trail suspension. It will never be as good as a true, modern motocross suspension for what you're doing. You might consider swapping to Honda CR forks. Several guys here have made the switch and swear by it, and have documented the required work here to help others.

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Im changing my tire now to a b403. I'm racing harescrambles, the series out here in Colorado incorporates mx into the harescramble track. So in not racing mx, it's just inherent in what I'm doing...but I bottom hard

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Im changing my tire now to a b403. I'm racing harescrambles, the series out here in Colorado incorporates mx into the harescramble track. So in not racing mx, it's just inherent in what I'm doing...but I bottom hard

 

   Then you need stiffer springs for sure. But you'd go to .46 or .47 probably. 

Edited by MindBlower

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I run 12psi both front and rear, just put the new M403 on yesterday. I tried to stop shipment on the springs but it was too late so I guess I'll put them in and see how they feel during my race this weekend. They are .47 springs; geared up I am almost 200# and I run a Clarke tank...usually only 3/4 at the beginning of the race but it's enough to where I don't have to pit for fuel (The races are 1.5 hrs). I wasnt aware some prefer atf, but I think I'll stick with the 5wt.

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I run 12psi both front and rear, just put the new M403 on yesterday. I tried to stop shipment on the springs but it was too late so I guess I'll put them in and see how they feel during my race this weekend. They are .47 springs; geared up I am almost 200# and I run a Clarke tank...usually only 3/4 at the beginning of the race but it's enough to where I don't have to pit for fuel (The races are 1.5 hrs). I wasnt aware some prefer atf, but I think I'll stick with the 5wt.

I run .47 on mine and they are perfect.  I'm 220, but a putt putt. If you ride hard and  bottom .44 you will like.  :)

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We would never use ATF,but maybe for racing ok.For rocks, roots,ruts,ATF beats you to death. I think 5wt good for what your doing,as far as bottom out shim stack mod wont help that.

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ATF is about 6wt. and is perfect in the earlier damper rod forks.  In the XR400 forks, you need a thinner fluid.  Use the adjusters on the top and bottom of the forks.  I think the bottom adjusters are for rebound and top for compression.   Too slow rebound dampening will cause your front wheel to wash-out on corners. 

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Its the other way around BR. Compression on bottom, rebound on top.

ATF is about 6wt. and is perfect in the earlier damper rod forks.  In the XR400 forks, you need a thinner fluid.  Use the adjusters on the top and bottom of the forks.  I think the bottom adjusters are for rebound and top for compression.   Too slow rebound dampening will cause your front wheel to wash-out on corners.

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Its the other way around BR. Compression on bottom, rebound on top.

 

 

This could explain why my buddy can't corner on the dirt roads.  He's a hell of a good single-track rider though.  Maybe I'll keep him in the dark.

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I was born and raised on the air cooled two strokes and there is nothing that can compare to those.  An under two hundred pound bike with 12 inches of travel, front and rear, 250 with as much snap as this XR400.  Ahh those were the days.

 

This thing is a tank.  You can't do whoops and double jumps and then expect it act like a pixey walking through the woods jumping logs over the trail.  Just ain't going to happen unless you really work at it.  Spent $1500 bucks on front and rear suspension mods and it really helped.    ....lighten the wallet and the bike still pretty much rides the same, like a friken tank.

 

It is what it is.  Learn to "ride" it and don't try to drive it.  I still bottom out the front end and can eat dirt going over a 6 inch log.  Just don't get your leg caught underneath it.

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If you had the suspension done (for any amount, not even $1500!)   and it wasn't a night and day difference, then something AIN'T right.  ;)

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Has anyone ever tried adjusting the oil level instead of jumping straight to heavy springs to keep from bottoming?? I see the 96-97 fork oil level is 100mm from top but the 98 and newer is 117mm from the top. I know the spring length is different between the 2 but why else would this be different between the years to make them run 17mm less oil? What if someone raised the 98+ level to say 110mm from the top (+7mm). Wouldn't that reduce the air volume and make the forks get stiffer quicker? I have some fork oil on order and I may try this just to see. I plan on removing the .46 springs I have in there now and dropping down to .42 and slightly raising the oil level. Might also do the shim stack mod but thinking I will try 1 thing at a time so probably not right away.

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