suspension revalve and high speed stability

[sluggo69]

first off i think that the kx fork mod is the best bang for the for kdx's. but my bike still gets kinda hairy at high speeds,especially on hardpack surfaces.though the forks do great on the trail and also absorb big hits a ton better than before i have to run them at almost full soft on both ends to keep the bike balanced and to keep the front from becoming too light.i spoke to jeff freddette and he suggested i speak to Drew Smith @ http://www.werproducts.net/ as the company to revalve my forks. what companies did you guys use to revalve your kx forks and how were the results? did it improve high speed stability?

my bike is a o3 200 and the forks are 03kx250 forks.


thanks,,wayne

[strider80]

What is the bike doing at high speed? The hits too hard? It may be more of a function of the front end geometry and shorter wheelbase of the KDX.

My somewhat unqualified advice:
Lower the forks in the triple clamps (where are they now?)
Buy a steering damper.

A revalve may help, if the high speed square edged hits are too hard the midvalve could be softened a bit (is your basevalve stock?). Hopefully Bradf will chime in.

My revalved basevalve seems to be working well for the lower forks speed hit, but I am still working out my midvalve.

[sluggo69]

my forks are stock and i have a scotts damper.its not the hard hits at high speed thats the problem . the kx forks take the hard hits with no problem.the problem is the front end tends to dance around and not stay planted at high speeds on rough hard pack. i know the kdx has a short wheelbase and is fantastic in the tight stuff. i just wondering if a revalve will be that much of an improvement to justify the 400-500$ investment. also im getting more into the racing side and its frustrating eating guys up in the woods only to have them catch up when the trails open up such as in ther grass track sections of harescrambles.

[strider80]

What height are the forks in the triples?

[sluggo69]

about a 1/2 inch or so as recommended by inda

[kawagumby]

Try revalving the compression stack yourself. Do a search, it is easy. I suggest just flipping the bike upside down and spinning out the valves with an impact wrench. Also, if you haven't already, make sure the spring rate is correct for your weight. There is no reason to spend big bucks to make your USD's adequate for 90 percent of what you ride. Also, most people need to readjust the rear shock to match the new front characteristics.

[wanaride]

If you do it yourself, don't compress the forks at all; the oil WILL come out.

A revalve service by a local suspension tuner cost me $200.

[bradf]

It sounds like headshake. If you have the correct rate springs, then lower the forks height above the triple by 1/4"(sliding the forks down through the clamps). I had mine at 1/2" extended up and the headshake was severe. 1/4" is perfect for mine. Also check the steering head bearings, be sure there is a slight amount of preload according to the manual. Sometimes the bearings are not seated all the way after a mod like this.

[krazyinski]

first off i think that the kx fork mod is the best bang for the for kdx's. but my bike still gets kinda hairy at high speeds,especially on hardpack surfaces.though the forks do great on the trail and also absorb big hits a ton better than before i have to run them at almost full soft on both ends to keep the bike balanced and to keep the front from becoming too light.i spoke to jeff freddette and he suggested i speak to Drew Smith @ http://www.werproducts.net/ as the company to revalve my forks. what companies did you guys use to revalve your kx forks and how were the results? did it improve high speed stability?

my bike is a o3 200 and the forks are 03kx250 forks.


thanks,,wayne

I did some shim adjustments on my forks and they worked great, I even have a stabilizer, but the little dance they do at highspeed does nothing to instill confidence, its not bad but makes the bike feel as if any second there could be some dirt sampling going on. after I took a buddys bike for a spin that was it I decided to bite the bullet and get pro action to do my suspension. My best advice is to have them revalved by a shop. I have yet to try mine out, I will thursday .

[skipro3]

I'm going to try a little different tack here and figure you have done nothing with the forks at all. (You said they were stock) Change the oil to a quality brand and set the oil level to the minimum amount recommended by the manual. Then go buy a decent front tire. I don't know what front tire you are running, but I've had real good luck with the S12's from Michelin. Lower tire pressure to about 6 to 8 PSI.
You might find that lowering the forks in the clamps (making them longer) and lowering air pressure in the tire helps on it's own. But, you should still change and set the oil level in your forks if you haven't already.

Finally, check your rear shock. It had a whole lot to do with how my front end behaved. Take the shock off, remove the spring and see if you even have nitrogen pressure by bearing down on it. It will be very stiff; almost impossible to move if it is anywhere near the right pressure. Set rear sag correctly too. Very important for high speed handling!!!

Anyway, these are just some other thoughts of why your front end isn't as stable as you'd like at high speeds. Bear in mind that the KDX is not a high speed machine. Dispite all those mods, I was always a little leary of anything over 50 mph. My buddies on their KTM's and Hondas could go 70+ and wait for me.

[Matt-itude]

Not to mention just suspension differences between the kdx and motocross bikes. the geometry and wheel base is probably the real culprit of the problem (if you call it that). the KDX design is completely different and it will never be as stable as the other bikes at high speed. Even when tuned to feel as stable it still isn't actually so. This of course is why it works so well in the tight stuff.

[canyncarvr]

You asked for recs for tuners. Specifically for USD forks.

I've had work done by MX-Tech in the past. That was on my OEM forks, NOT my USD forks. Still, I would suppose J.Wilkey knows more about the USD setups than RSU setups.

It wasn't at all cheap. Shipping is a hassle. Still, MX-Tech did what I asked, was open to communication during the tuning process after I got them back, and repeatedly assisted me in getting to where I wanted to go fork/spring-wise.

You don't live so far away from them..shipping would be less.

I understand the responses for 'do it yourself'..but if you simply want to send them in (what you asked about) MX-Tech is an outfit I would trust again on my KX forks if I sent them off somewheres.

Let us know what you get sorted out!

[krazyinski]

Not to mention just suspension differences between the kdx and motocross bikes. the geometry and wheel base is probably the real culprit of the problem (if you call it that). the KDX design is completely different and it will never be as stable as the other bikes at high speed. Even when tuned to feel as stable it still isn't actually so. This of course is why it works so well in the tight stuff.

OH now I wouldnt say that, mine was very stable at high speeds with the revalved OEM forks as long as you didnt hang somthing.

I didnt know my lower shock bearing was toast and that could contribute to the KX forks sketchy feel.

The sad thing is I know better, ITs point less to tinker around when you know that a proper valve job will cure the issue. This was one of the first things I used to do when getting a new bike.

I relate it to jetting, you must know what you have as a base line then go from there. you cant jet by changing fuel/oil ratio and using hotter/colder plugs thats crazy.

If your trying to get your 7 year old shock and some forks you got from some one that you dont know to work right, then your flying BLIND.

[Matt-itude]

rerading my post I think it sounded wrong. I didnt mean it is pointless to improve on what you have. I was just saying even when it feels right it wont take as much to throw you out of shape on the kdx at speed.

[sluggo69]

i lowered the forks to about 3/8 in. from about 3/4 in and it helped stability alot. i tested it on a local mx track today and it was a big improvement.here is a video of the track

http://mxrevelation.com/videos/2007/V-RYAN.RAIFORD.zip

i have decided to go ahead and have the forks done by drew smith at wer as recommended by jeff freddette. drew said he would do it for 350-400 bucks plus shipping.i will keep you guys updated with the results. thanks for all the advice.
ps who says kdx's dont belong on a mx track.the only jumps that gave me problems was the last two big tabletops in the video.i was hitting them in forth at aout 3/4 throttle and kept coming up about 10 or so feet short. this was my first time on a mx track so im satisfied. it was fun as hell but damn im gonna be sore tomorrow lol

thanks,,wayne

[canyncarvr]

Already said...but I don't understand using a tuner that you don't know (neither does anyone else) when other tuners are known factors.

Re: Stability in general.

With both OEM and KX forks (up .775" in the clamps) my bike is nothing if NOT stable as fast as I can go..which by GPS is well over 70mph.

I realize what one bike does has nothing to do with what another doesn't. My brother-in-law had headshake trouble with his KDX (same year, same mods as mine) that never got resolved. Well, he resolved it with a punkin.

A thought...have you recentered the front wheel..reset the forks? You are familiar with the process?

How did you measure the fork placement in the clamps.

What is your steering head bearing seat procedure?

'Re-align' your frontend. That includes steering head set, clamp torque, wheel center and fork placement...with a set of calipers maybe. You should be easily within .001" left-to-right.

[fuzzy]

I will add that I've heard a lot of good things about WER's valve jobs....They tailor to woods guys for the most part. That being said most forks that are setup great for the woods will suck at high speed. Ever see the GNCC race at Wisp ski hill in MD? Those guys take this huge uphill jump, and half the bikes crash on landing...At the same time through the rocks the boingers were going crazy....Can't have it all. Did you specify exactly what you wanted out of the forks when you sent them?

[canyncarvr]

Everyone pretty much knows the drill. Any long-distance tuning method has a close to zero chance of success. Even if the tuner has a clue AND is told exactly everything he needs to know to get the job done, there will likely be some fine-tuning required.

That's where a local tuner is a good idea. One around here will 'do' your suspension. If you don't like it, tell him what you don't like and he will change it. If you STILL don't like it, he will COME DOWN to ride with you, to observe what's going on so he CAN fix it.

Well...obviously a rider being the problem (good chance of that) isn't going to be resolved with a shim stack configuration change.

I know nothing of WER's revalves. Their damper is pretty much a waste of time, why would their valving be any good? But..what WER does and what this 'drew' guy does do not necessarily have anything in common.

And I haven't even started to gripe about their dampener!!

Cheers!

[kawagumby]

Drew Smith 20 time ISDE competitor....known in the industry for his off-road suspension setup prowess....sounds like a good choice to me if you are willing to send them out.

[sluggo69]

im gonna take the advice and use a local tuner. pro-action has a local guy. he comes highly recommended. anyone use pro action?