Did I build my forks right?

[mnnthbx]

I just changed my fork springs. It's all new to me, so can someone varify I did it right?

Oil level = I filled w/ 7wt.. After bleeding the air, the level measured 110mm from the oil to the top of the tube.

Pre-load = The service honda xr 400 springs were exactly 0 preload (no slack either) with only the clip in washer on the bottom of the spring. Once I added the top washer, and a second OEM top washer flipped over, the pre-load was right at 3mm.

Thanks for the help.

 

[mnnthbx]

Well, I went ahead and buttoned it up. Bouncing around in the garage I noticed two things (it may have always been this way & I never noticed)

1 - There is a bit of "sticksion" early in the stroke when I compact the front end.

2 - There is a noise that sounds like the springs rubbing the inside of the fork.

I'm not sure if either of these things are detrimental or not. Thanks for any comments. Greg.

 

[mnnthbx]

I made it to a friends house and checked his brand new stock KDX. His has a bit less sticksion, and none of the rough noise. The noise isn't right for sure. I hear it when I compact the fork deep into the stroke. Again, it just a rough "spring gringing on something" sound.

After looking through the shop manual, the only thing I see different is that I use the two flanged washers that were on the ends of the stock spacer to pre-load the XR springs. I have one flange turned down into the top of the spring, the other flange faces up into the top plug. In the stock set up, both flanges faced into the spacer.... Could this be the cause?

 

[mnnthbx]

Have I been black balled or what?

 

[canyncarvr]

I've read it a couple of times...I'm still not sure what is facing where. IF I understand correctly...

Change that top flanged washer. Consider that you are no longer running a flat washer against an aluminum cap but a small ridge of metal.

Not good.

In any case, run the 'flat' of the washer against the cap.

That noise you speak of (if I'm understanding it correctly) is common. Instead of turning the fork cap when you put it on, HOLD it and turn the tube to tighten.

Sounds like you're close to the 530mm length. Preload is a matter of preference (I'm running a bit over 3mm).

IF you have the top flanged washer upside down you will get the same preload number if you turn it the correct way (flat part against the cap), cut a small piece of PVC the length of the two flanges..that will be about 4mm. Cut it on a table or mitre saw. You can do it by hand that thin if you're willing to do a lot of filing..and that filing is hard to do 'cuz it's so thin!

Well, I'm assuming you cut by hand not a whole lot better than I do. Maybe YOU'RE good at it! ;)

You end up with the flat parts of the washers against the spring&cap...the PVC piece held by the protruding parts....just like it was with the long steel tube. If you must lose one of the washers, I'd lose the top one..let the PVC ride on the cap, the single washer on the spring.

You may end up somewhat over 3mm. My choice was to keep the washers and have a bit more preload than I'd prefer.


Don't know about the 'stiction part. Maybe it was there before..maybe you are feeling the floating rotor? That's happened before.

Good Luck!

Let us know how it works out.

But...how do you like the spring part of the spring job? I'd like to hear about that, too.

Cheers!

 

[mnnthbx]

Thanks alot CC. I'll start tearing it down. I will make the smallest spacer possible to hold the washers flange to flange, and twist the tube at assembly.

Let me also say, the time you (and others like you) spend "schooling" us, on redundant questions, does not go unnoticed. Thanks again. Greg.

 

[GS]

Hi there,
Question for the learned..which fork spring (part#, year of xr400, spring rate..??) did you install? I really need to do something soon about my mushy mushy forks and would like a part number or some direction as to which spring to use and where to get it. I, unfortunately, weigh 220-230# and am not aThanks are in order if you can help point me in the right direction. By the way "sticksion" should be just as much a real word as "gripsion", in fact we should all these to our spell-check dictionaries. Don'cha think?
Greg

 

[GS]

try again.......
I meant to say that I weigh 220-230# and I am not a really aggressive rider in the rough stuff. Hate the pain of falling offf too much!
Greg

 

[canyncarvr]

Seems mnnt said he was around 200#. At that I'd guess the .40kg/mm spring to be a bit on the light side. I can't imagine they'd be any good for 220#.

You might try a look at the racetech site. You're looking for a 36mm spring. You can get a .43 spring for a 650R, but it's not 36mm. Besides I have no idea how long that spring is.

I've only looked into .38s and .40s from Honda. A knowledgeable shop should be able to sort out what Honda springs 'fit' into the 530mm long, .42 or so category.

It's not the name Honda that's the issue. It's an oem spring (hotwound) that is about the right size (36x530mm) to fit in the kdx tube without almost 4" of metal spacer.
***edit***
The whole point of hotwound comes from conversations I had with Mr. Wilkey @ mx-tech years back. He'd just gotten back from some 'spring convention' or somesuch and was pretty excited about what he'd learned about hotwound (oem generally) vs: coldwound (aftermarket). I'd just discovered a spring failure on my bike (new eibachs from mx-tech that had 'shrunk' about 1/4" inch in a couple rides). He (Wilkey) said the failure rate on cold wound springs was quite a bit higher than hotwound..but the expense of making hotwound springs made it unreasonable for an aftermarket mfg. to make springs for every bike in the world. That's a large reason I went the Honda route.

But then you notice that the mx-tech site's first word used to describe their springs is 'coldwound.' As interested as he (Wilkey) was in the hotwound idea, I don't know why he didn't go that route. Expense maybe. I've never asked about it.

Anyway...food for thought......or for throwing out! Your choice.
********

Another option, talk to mx-tech for a recommendation. Ask them about a spring that fits that spec. That said, the mx-tech site does list the .40 spring in your bike for your weight. Seeing as that's the same spring they list for my case and I'm more'n 50# lighter than you...you kind'a have to wonder if that's the biggest spring they have, 'eh? ;)

 

[carlrf]

Fork Springs

:cool:
Howdy, I am new to the KDX, arena however not new to BMW street bikes, CZ Vintage MX and Trials.

My question/comment is, how come nobody uses the "Progressive" brand springs? I have always had success with them and just put a set with new seals and oil in a 95 KDX200. Seems a lot better but what do I know? :yikes:
carlrf

 

[canyncarvr]

It's my understanding that progressive springs (not brand..but type) have an inherent problem. If 'x' length of the spring is wound for 'soft' then that mathematically necesitates that there is only 'length-x' left for the stiffer stuff.

As spring length decreases its linearity goes away, it's rate increases with given compression distances and its load capacity decreases. Besides if you're in coil bind in the 'soft' coils before you start compressing the 'stiff' coils..well I doubt that's a good thing.

Maybe that's all bs. That is they way it's been 'splained to me..and it makes sense (uh-oh!), too.

If they suit you, they sure as heck tickle me!

;)

 

[mnnthbx]

So here's an update.

I took the forks back out, added a thin PVC spacer with the flanged washer facing into the PVC, added some oil to get @ 110mm. (I assume the fresh oil had settled + i pulled the springs out and lost a bit).

Total preload with washers is around 8mm. Oil is Bel-Ray 7wt. I weight 198lb. and ride a moderate pace over very rough terrain.

My "sticksion" problem does seem to be a floating rotor issue, so thats resolved.

My noise situation remains. The left fork is quiet and smooth. The right fork has a "click" in it 2/3 into the stroke. I have disassembled it twice, and to my knowledge, there's not enough parts in the fork for much to be screwed up, so I guess I'll just live with it. It has no noticable effect on the bike, other that the "junky" noise. They may just be how forks are???

As for performance, I live on a small farm, and have a trail we time each other own for kicks. It has a big flatlanding jump, as well as a small amount of roots.

The bike is more solid taking the big hit off teh jump. Mid speeds I can't tell much. ( I have 10 minutes on the set-up). Slow speed roots now are unnoticed, and the bike felt more stable on a big down-hill. It may not be the end-all mod that I've read about (I blame this on my limited ability and needs), but I think it is worth every cent I've spend to do it.

One other questionn stupid I'm sure... I don't bleed all the air out do I? just relive the presure while on the stand?

Thanks for your help, and any ideas on my noise is appriciated.

 

[carlrf]

It's my understanding that progressive springs (not brand..but type) have an inherent problem. If 'x' length of the spring is wound for 'soft' then that mathematically necesitates that there is only 'length-x' left for the stiffer stuff.

As spring length decreases its linearity goes away, it's rate increases with given compression distances and its load capacity decreases. Besides if you're in coil bind in the 'soft' coils before you start compressing the 'stiff' coils..well I doubt that's a good thing.

Maybe that's all bs. That is they way it's been 'splained to me..and it makes sense (uh-oh!), too.

If they suit you, they sure as heck tickle me!

;)

:cool: Hey, that's great. It's more than I new before. Actually it sounds famliar after you said it. Maybe I will try the straight weight springs on the 220. However they don't feel near as soft as the 200 did. Maybe someone has been in there already!
Thanks
carlrf :yikes:

 

[GS]

CC Thanks for addressing not just my question, but others on this site as well. Seems like there just might be lots of pretty good stuff in that noggin of yours! Maybe my style of riding wwaaaayyy back on the seat will work with those lighter spring rates. 'eh? to you too!
Greg

 

[Jackpiner57]

For what it's worth, I put in Fredette .42kg springs and I like them. I weigh 210 and ride fairly agressively. They are good in the eastern woods and rocks too.

 

[canyncarvr]

re: let air out.

Covered this already? Right?

That air shock (air space at the top) is a big deal when it comes to your forks performance. I found the MotionPro bleeders to be a huge benefit to my riding enjoyment! The pressure varies a whole lot over the timespan of a single ride...not only due to temperature and outgassing, but elevation, too!

I bleed my forks (the MotionPro poppers) at least several times a ride. Maybe six..maybe ten. Why? Because it makes a great big, fat difference in the way my bike handles.

Besides, you can kind of tune that air shock by using a 'negative' pressure, too! The distance the forks are compressed when you bleed that air out will make a difference.

Don't know about the noise. As long as that clipped-on washer is on the bottom, the forks were clean when you put 'em back together I wouldn't worry about it a whole lot. Maybe when you replace your sliders sometime in the future (read: take the things apart and really clean them up) you will find the noise is gone.

Enjoy your new springs!