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XR 400 Front forks, harsh, beating me to death

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When I rebuilt the entire bike, I did the front fork compression shim mod, removed 6 shims from each side, while installing new fork seals. I weigh about 205. Rear sag is set. I know the front forks are way under sprung for my weight, and that I need new front springs. But I am wondering if new springs will fix what I am feeling or if there is anything else I need to do. The forks feel like they lock up on small bumps, rocks and roots. I have read that they will hydraulically lock up. I am wondering if this is what I am feeling. They beat the crap out of me.

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Hydraulic lock up is when the fork oil height in the tubes is too high, leaving not enough air cushion space. You compress the forks enough to blow thru the air cushion, and since you can't compress a liquid, the forks feel like a solid tube from there. When you refilled the forks with oil you should have set oil height to 4.6".

Yes, new springs will fix your problem. With the stock soft springs and your weight, the springs start out compressed far into their length. Any handling of the terrain starts from there, whether its g-outs, bumps, roots, rocks, making them very harsh feeling. in extreme conditions, You may even be getting coil bind.

Have you replaced the rear spring for your weight? What kind of sag numbers do you have it set to, Free sag and rider sag?

A too soft rear spring that you have to over-preload in order to get the proper rider sag will cause weight to be transferred to the front suspension, compounding the problems of its too soft springs.

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4 minutes ago, Trailryder42 said:

Hydraulic lock up is when the fork oil height in the tubes is too high, leaving not enough air cushion space. You compress the forks enough to blow thru the air cushion, and since you can't compress a liquid, the forks feel like a solid tube from there. When you refilled the forks with oil you should have set oil height to 4.6".

Yes, new springs will fix your problem. With the stock soft springs and your weight, the springs start out compressed far into their length. Any handling of the terrain starts from there, whether its g-outs, bumps, roots, rocks, making them very harsh feeling. in extreme conditions, You may even be getting coil bind.

Have you replaced the rear spring for your weight? What kind of sag numbers do you have it set to, Free sag and rider sag?

A too soft rear spring that you have to over-preload in order to get the proper rider sag will cause weight to be transferred to the front suspension, compounding the problems of its too soft springs.

I still have the stock rear spring. I set rider sag to about 4 inches. The adjustment was all the way at the top when I started, not sure it had ever been changed. I figured the rear was good since I could preload the spring and get the sag right. Sounds like I need a new rear spring as well.

 

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9 minutes ago, Paxtonspeed said:

I still have the stock rear spring. I set rider sag to about 4 inches. The adjustment was all the way at the top when I started, not sure it had ever been changed. I figured the rear was good since I could preload the spring and get the sag right. Sounds like I need a new rear spring as well.

 

Is 205 your every day street weight or your outfitted to ride weight? For the rear spring to be right for your weight, with 4" of rider sag you should be seeing near an inch of free sag when you right the bike off the kickstand, with it under just its own weight.

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27 minutes ago, Trailryder42 said:

Is 205 your every day street weight or your outfitted to ride weight? For the rear spring to be right for your weight, with 4" of rider sag you should be seeing near an inch of free sag when you right the bike off the kickstand, with it under just its own weight.

205 is my regular weight, no gear on.

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23 minutes ago, Paxtonspeed said:

205 is my regular weight, no gear on.

Always, when selecting a new spring, figure correct spring rate using your geared up and ready to ride weight. Same for setting sag.

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30 minutes ago, Trailryder42 said:

Always, when selecting a new spring, figure correct spring rate using your geared up and ready to ride weight. Same for setting sag.

205 is my Covid weight. Hoping to lose a few pounds...😂. Usually in the high 190s.

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Trailryder42 has given some good info thus far.   I will add a few things.  Just as important as race sag (you on the bike) is free sag, the bike under its own weight.  If you have too little free sag, and I will venture to guess you do, the rear will not work correctly causing a rough ride.   Your rear can affect how the front feels as well.  Confirm that both your rear race sag (you on the bike) and free sag (bike under own weight) is correct. 

In addition, too soft of fork springs can produce too much sag in the forks which puts the bike into the mid valving too soon causing a harsh ride.  I had this exact problem on a TE450 I was setting up for myself some years back.  Some cheaper aftermarket seals and wipers also can cause excessive friction on the tubes in my experience.  OEM or SKF only.   Lastly, if your bushings are old, consider replacing.  Seals, wipers, and bushings all can attribute to harsh feeling forks.  

This is assuming you put your shims and fork internals all back together correctly, are using the correct oil weight, and at the right height.  Height is with the internals in, no springs, and tubes collapsed.  

Edit - also make sure that adusters are fully out when assembling.  You will need to reset them after assemblying anyways.   A lot of this you may already know, apologize if so.  Just covering all the bases.  

Racetech may not carry the proper springs rates for you anymore.  Cannon Racecraft out of Oklahoma does.  They can provide just about any rate you need.  

Edited by Captain.Olives
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This good info these guys are giving you . To add to this do not use racetec springs in xr400. They are ill fitting  caused us many problems. Cannon is great company use there springs

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12 hours ago, Captain.Olives said:

Trailryder42 has given some good info thus far.   I will add a few things.  Just as important as race sag (you on the bike) is free sag, the bike under its own weight.  If you have too little free sag, and I will venture to guess you do, the rear will not work correctly causing a rough ride.   Your rear can affect how the front feels as well.  Confirm that both your rear race sag (you on the bike) and free sag (bike under own weight) is correct. 

In addition, too soft of fork springs can produce too much sag in the forks which puts the bike into the mid valving too soon causing a harsh ride.  I had this exact problem on a TE450 I was setting up for myself some years back.  Some cheaper aftermarket seals and wipers also can cause excessive friction on the tubes in my experience.  OEM or SKF only.   Lastly, if your bushings are old, consider replacing.  Seals, wipers, and bushings all can attribute to harsh feeling forks.  

This is assuming you put your shims and fork internals all back together correctly, are using the correct oil weight, and at the right height.  Height is with the internals in, no springs, and tubes collapsed.  

Edit - also make sure that adusters are fully out when assembling.  You will need to reset them after assemblying anyways.   A lot of this you may already know, apologize if so.  Just covering all the bases.  

Racetech may not carry the proper springs rates for you anymore.  Cannon Racecraft out of Oklahoma does.  They can provide just about any rate you need.  

Thanks for all the info, I am going to get the forks straightened out, then move to the rear. The fork bushings were in good shape when I tore them down. I used the factory manual when I rebuilt them. I am not completely green on fork rebuilds. I used to have an XR650R that I did fork rebuilds on.

I used Bel Ray 5 weight in them, filled with forks collapsed, no spring. I sucked the extra out with a homemade fork oil level tool and a hand held vacuum pump. The level is set to the factory spec. The shim mod was pretty straight forward.

I did read somewhere on another board where guys were running the compression clicker all the way out, all the time. I also read about removing 8 shims, instead of 6. Any input on that?

Edited by Paxtonspeed

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6 shims removed on forks with 12 shims good. We use 3wt rear shock oil for our riding . Rebound is set full hard then out ,4 clicks. For our riding 5 WT ,oil too stiff we use .43 springs . Oil level between 4,in to  3.  3/4. Ultra plush  no bottom out

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1 hour ago, Paxtonspeed said:

I did read somewhere on another board where guys were running the compression clicker all the way out, all the time.

It would depend on the type terrain you plan to see and the wt. fork oil You used. With a heavier oil, you'd need to run the clickers closer to full soft to get any oil flow thru the valving to produce damping for anything besides a flat road.

I think you're better off running a light 2.5 to 5 wt oil to have some range in compression damping. A lot of folks ride varying types of terrain and need to be able to adjust compression and rebound accordingly. Example: I have 2 local riding areas. one is pretty much sand and whoops, the other hard pack technical, hills, rocks and such. If I left my suspension set up for riding the hard pack area and then tried to ride the sand area, it would be a difficult ride with the suspension set so plush. Sand riding requires stiffer/less compression damping of the suspension to ride well.

With ride time and experience, I learned how to set my compression and rebound for one area, then with just a few clicks here and there, could ride the other. For areas that are a mix of terrain types, you figure out a compromise in your settings that you find acceptable for all around riding, set it and forget it until you ride something more specific.

Pretty much what we have to do with the XR suspension, it being pretty low tech compared to modern stuff, with all the different kinds of damping circuits, high speed, low speed, mid valves, transition, etc. of today. 

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13 minutes ago, Trailryder42 said:

It would depend on the type terrain you plan to see and the wt. fork oil You used. With a heavier oil, you'd need to run the clickers closer to full soft to get any oil flow thru the valving to produce damping for anything besides a flat road.

I think you're better off running a light 2.5 to 5 wt oil to have some range in compression damping. A lot of folks ride varying types of terrain and need to be able to adjust compression and rebound accordingly. Example: I have 2 local riding areas. one is pretty much sand and whoops, the other hard pack technical, hills, rocks and such. If I left my suspension set up for riding the hard pack area and then tried to ride the sand area, it would be a difficult ride with the suspension set so plush. Sand riding requires stiffer/less compression damping of the suspension to ride well.

With ride time and experience, I learned how to set my compression and rebound for one area, then with just a few clicks here and there, could ride the other. For areas that are a mix of terrain types, you figure out a compromise in your settings that you find acceptable for all around riding, set it and forget it until you ride something more specific.

Pretty much what we have to do with the XR suspension, it being pretty low tech compared to modern stuff, with all the different kinds of damping circuits, high speed, low speed, mid valves, transition, etc. of today. 

In Ky, its pretty hard packed, rocks, roots, woods riding.

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We have everything In Baja even snow haha. This place can.beat you to death the xr4 forks.with 3 WT ultra plush roots rocks ruts woops Forest beach swamp 

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7 hours ago, Paxtonspeed said:

Thanks for all the info, I am going to get the forks straightened out, then move to the rear. The fork bushings were in good shape when I tore them down. I used the factory manual when I rebuilt them. I am not completely green on fork rebuilds. I used to have an XR650R that I did fork rebuilds on.

I used Bel Ray 5 weight in them, filled with forks collapsed, no spring. I sucked the extra out with a homemade fork oil level tool and a hand held vacuum pump. The level is set to the factory spec. The shim mod was pretty straight forward.

I did read somewhere on another board where guys were running the compression clicker all the way out, all the time. I also read about removing 8 shims, instead of 6. Any input on that?

👍 you never know who you are conversing with here, their experience, or understanding.

If folks need to run their clickers full out all the time......  there is something wrong with their forks or they are valved and/or set up incorrectly for their use.   

I'd have to go down to my workshop to verify how many shims I removed from the 99 XR400r, the oil height, and my clicker settings (they are not full out.)   Its been some time and I honestly don't remember other than following the basic formula posted on this forum.  I do know the forks are using Honda 5wt and the height is higher than stock to provide better bottoming resistance on high speed g outs. 

I'm no pro suspension tuner, but I have set up or worked with pro's setting up a lot of bikes over the years and do all my own rebuilds.  So I've got a decent understanding of them and experienced the difference between bad, acceptable, good, and great suspensions.  The XR is one of the few bikes I didn't have a Pro revalve as I was satisfied with the with the shim stack mod I accomplished following others here.   Mine is used almost exclusively for my SoCal and Baja desert trips.  So my speeds are much higher and the terrain different than what you are attempting to tune for.   I ride my two stroke YZ at home in NorCal, and its tuned for rocky slow technical trails.... stuff the XR would be no fun on as set up.  

There really isnt a magic shim stack formula, everyone has their preferences.  You may need to modify further or even bandaid it with lighter fork oil for a short time while figuring out your preferred stack.  Bunch of good stuff online about cartridge fork tuning and shims.  It may take more than just removing a few shims and instead actually changing shim thicknesses (that would be my guess if I were tuning my own for the woods.)   If you have a good relationship with a pro, he may even provide suggestions and or just modify the cartridge stack for you without requiring the full fork.  

Its just my process, but I always start with the rear.   Its been my experience that the rear really can affect the front feel more than the front affects the rear feel.  What sometimes feels like what should be a front issue is actually the rear being way off.   That's just been my experience on a couple of bikes and I am by no means a pro.  

Good luck and hope you follow up with your final set up.   Good luck!

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Yep; where to start is the big question. I suggest opening one fork and recording the shim stack and then post it and ask questions, you will get answers. The shock is a bit more of a problem which is why CO likes to do that first. My thoughts are similar as the forks, but to save time assume the shock is stock and ask for recommendations.

The shock is pressurized to reduce fluid cavitation so it needs to be recharged. Most try to find nitrogen gas and a lot of tire shops have it, but they may not have a regulator that will go to the pressure you need. I recharge with CO2 because it is inert and I have it, a regulator, and a no-loss chuck. My reg doesn't go past about 140psi but that seems to be enough on the XR shocks.

A lot of folks just suggest removing every other compression shim and that does soften up compression by a bunch. I've taken a different approach and use a 2 or 3 stage stack. Google can be your friend.
Rebound shims need to be selected to control the rebound of the springs used, so if you change springs the rebound probably needs to be changed.

Fluid viscosity makes a difference and cartridge forks like the XR400 use different fluid than the old damper rod forks, also shocks use a different fluid. Peter Verdone Wiki page has info on suspension fluids. https://www.peterverdone.com/wiki/index.php?title=Suspension_Fluid

 

Edited by Chuck.

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This is real good info like captain says he is riding faster routes. We ride in Baja the tight horse trails. Slow speeds they seem to do speed ok. Not a strong point of the xr. I also beg to differ on adjuster all the way out. As it does not matter how you get there. It only matters how it works ours  . Are ultra plush  that lets us old guys ride 8 hours in the saddle . Good luck to you.

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On 7/7/2020 at 8:24 PM, bajatrailrider said:

This is real good info like captain says he is riding faster routes. We ride in Baja the tight horse trails. Slow speeds they seem to do speed ok. Not a strong point of the xr. I also beg to differ on adjuster all the way out. As it does not matter how you get there. It only matters how it works ours  . Are ultra plush  that lets us old guys ride 8 hours in the saddle . Good luck to you.

Totally agree, it only matters how it works.  👍  I should have said, if you have to run them full out.... you could be modifying the valving even more to soften.  I like to have some adjustment left either way with my clickers.  Kinda like a fuel or air screw on the carb.  You could get them to run well at one extreme setting or the other, but change to the right pilot jet for conditions and you get the sweet spot in the middle with the air/fuel screw leaving further adjustment available down the trail in either direction (if that makes sense.)  Ultimately, if the rider is happy with the set up, thats all that matters however you get there.  

XR's of all kinds are cool as hell... old school now.  Funny, two years ago at the Barstow to Vegas event I was admiring some young 20 something year old's bikes.  They were running and having a blast on some old vintage TT500's.   They said they had actually been admiring my old school XR400r with the retro race light that day.  Thanked them for the complement, then I laughed to myself... realizing that the XR really is old tech now.  Hadn't ever really looked at it that way myself or thought of it as retro until then.  😄

I havent had a modern 450 for 6 or 7 years now.  My primary riding is more suited to small bores and two strokes, so sold the last one I had and went back to an XR for the annual Baja trip, occasional SoCal desert run, or dual sport day.  Less money sitting in the garage unused for so many days a year.  

For the money, they are cheap to acquire and set up.  Rock solid, reliable, easy to maintain or forget about... and inexpensive to repair or rebuild.  Very capable too if you set your expectations correctly.  They will never be a new Beta or Ktm/Husky 350.   You can certainly run all day with friends on modern bikes, just dont try and make one into a modern bike.  Optimize them within a budget and enjoy it for what it is.  

I was reminded of that on this past winter's trip.  My bike is optimized for sandy two track at moderate speeds for most of our trips, was ok on Window Rock and some of the single track between Catavina and El Rosario.  Skipped the Rockman trail some of our group rode because I simply didnt want to get beat up and at 51... old enough to know better.  Got thrashed on one of the rocky hard routes getting to Mikes from the south at 10pm in the dark.   

We never plan on riding at night, but after dealing with a medical emergency for one of our riders we ran out of daylight.  The most direct and fastest route was going to be the rockiest climb up to Mikes.  Nothing dangerous, just not enjoyable, and took more energy, especially at night even with good lights. 

Got me thinking about a modern bike again for the trip, maybe a 350 if the budget ever presents itself.  

Where do you folks generally ride in Baja?

  

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Cap I live one hour past Ensenada south . Great single track. Pm me in advance before your next run. Will show you the shit. I have to agree the xr4 is best all-round Baja bike. I'm riding smaller bikes now as old age. I ride every week still like the hard stuff. Rockman trail did it once never again. Just pounding boulders no fun. I was the only one that did not break off shift lever or foot pegs hahaha . Or go nuts but close to it. 

 

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