Wishy washout front end...Will springs help????

[vandean]

I know there is a lot of talk about the front end being soft on the KDX but can anyone clear this up for me?
I weigh just about 210lbs so I realize I need heavier springs; so which ones and is it going to correct what I have been experiencing so far?
I rode this thing three times so far and from what I have gathered thus far is that I really love the power of this bike however the front end leaves a lot to be desired.
I've ridden in three different types of terrain thus far and from each ride I seem to experience the same eery feeling.The most uninspiring feeling I've yet to experience with any dirt bike.It all comes from the front end .Riding in woods trails the bike is great until you come across anything resembling soft or loose soil or mud.The front end just wants to washout everywhere.The same applied the second ride in deep loose sand except only worse.This thing goes wherever it wants! No control at all.I just sat and watched the guy on his YZ426F rip through it like he was on solid ground.I realize the power difference however this thing has enough power just no front end.The last ride today was on a motoX track.Forget it.Nearly bit it from the front fender constantly wacking the tire.Nearly killed me.The sand in the berms again washed out the front end and some trail riding today as well told the same story.The muddy ruts were a challenge that should have been a lot easier if the front end would just go where I wanted it to.I used to own a Rm 125 and that thing went wherever I pointed it!
Well , will springs help, or should I find a KX250 front end(don't know if it would fit anyways) or should I get another bike altogether.It's an 02 220 and I like it very much,just want to feel more confident about riding it.One last thing.The amount of flex when you grab the front wheel between your legs and push on either side of the handlebars seems way to be way too much.Is this front end too weak for my bodyweight?Seems to have a far too flexible set of forks.Oh by the way losing weight is not what is required for those that may have been thinking of suggesting so! I am a very solid 210 so keep your Jenny Craig or Richard Simmons wisecracks for the fat chicks!!!!!
Just want to make this thing enjoyable to ride so I would value your input.

 

[Fred T]

Well, I would suggest you get a set of .44 kg springs for it from MX Tech. You may also want to consider a 5.2 kg rear shock spring. Try that as a starting point along with puttung Mobil 1 ATF in as fork fluid.

 

[canyncarvr]

That 'flexing' stuff in the bars is what keeps your hands from going to sleep after 10 minutes. The kdx has a fairly soft set of bushings the bar mounts go through. Higher durometer bushings are available. Scotts makes some.

Other than that...there's no way a stock sussed kdx is going to hold up to 210#. 44s/5.2 sounds close to me.

You can put a kx front-end on a kdx. Sage did. That info is posted on this forum. It's not something you bolt on in ten minutes.

Curious what your sag is set to........???? Bet it's over 100mm !!;)

 

[Braahp]

Anything over .40kg springs will beat you to death in the woods..........ask Fredette. I weigh 225 and use the 22lb(.39kg) and its perfect. Not sure if springs will help what your experiencing though. It will definately get rid of the major nose dive going into corners on the front brake. I know they are pricey but check into a steering damper. Will solve all your wishy washy frony end problems. One of the best things I ever put on my KDX for sure. Inspires confidence like you wouldn't believe.....and it should cause your front end will be straight and true with one.

 

[vandean]

My sag is at 100mm.The first thing I did when I got the bike home was to tear apart the rear linkage and regrease it,set the sag and relube the steering head.What will the front end hold up to if not 44's.I see Fredette recommends around 23lb whick sounds to be around the same!
Wher did Sage post the info about his front KX install?

 

[vandean]

Braahp.Do you mean the steering damper will make the front end straight and true or are you referring to a fork brace?
What did yours cost?

 

[Robcolo]

Vandean - I just recently got a 220 and have exactly the same complaint - you absolutely cannot trust the front end! Anyone who's gone fast on another bike with great suspension [like my KX 250s] feels it immediately. Mine mostly washes [understeers] but will also knife or oversteer on occasion. Guys are blaming it on the springs but a soft spring will have the front low and should eliminate understeer. Unlike you I weigh 123lbs. I'm looking at revalving as the high speed compression is way too high and I feel that the front tire is simply skipping around after hitting bumps.

 

[vandean]

The revalving might be required for myself as well.I'm going to start with the springs first. I have experienced oversteer also.I wouldn't mind a Scott damper if anyone has a used one.Their just so damn expensive new.I would rather just replace the whole front end period!

 

[MassKDX]

I put in new .42 springs from MX-Tech w/Mobil ATF in my KDX along with adjusting the sag and a new front tire. All of the front end wash has stopped for me. I think you will be amazed when you put a new set of springs in your forks. They make one heck of a difference. I have not re-valved yet but I do plan on it in the near future. :)

 

[vandean]

Thanks I'll try that first.My front tire is new . 02 220.

 

[canyncarvr]

..but a soft spring will have the front low and should eliminate understeer

Control of the frontend comes from the rebound action of the forks. Too much rebound damping (too slow) and it will cut (low side) too little (too fast) and it will wash (high side).

That's not my idea. Check any suspension site any you'll read that.

Given the kdx doesn't have rebound damping (well, in stock form), the idea can be transferred to a too-soft spring. If it's riding low cuz it's not up to the task, it also will NOT be giving you any 'push' or rebound. Guess you could look at that positively as 'eliminating understeer' or negatively as 'increases oversteer';).

How about it's just right from the gitgo? No, I sure wouldn't want to ride with .44s, but that's close to 'the book' from some tuners for #210/no gear (I assume. Vandean said 'I weigh...'). I'm 180-or-so, and I thought .42s were AWFUL! But, you won't find me on any moto-track, neither!

Go with what you know! A stock kdx is NOT setup for a #210 rider. So, fix it!:)

Glad to hear your sag is set. I'll wager most bikes aren't. Hhmmm...what's your free sag? At 210#, is it over an inch? That's a 'too light' rear spring indication.
***edit***
A misspeak. An error. Brain flatulence. Free sag OVER an inch is indicative of too heavy/strong a spring.

Correctly stated would be:
At 210#, is it less than 1/2 an inch? That's a 'too light' rear spring indication.

 

[kdxjr]

3 rides, check your air pressure should only be about 10 psi front and rear. A good soft terrain front tire would help. Use the rear brake only in loose corners, front brake will make it lock up easy and wash out..Keep the RPMs up in loose stuff like sand or mud if your not going forward in it your going down. Find a place and practice slidding with rear brake and gassing it hard. Learn to do this in corners..
my 2 cents take it or flush it..

 

[Fred T]

Originally posted by canyncarvr


Hhmmm...what's your free sag? At 210#, is it over an inch? That's a 'too light' rear spring indication.

CC
You wanna explain that one a little? If you are heavy I'd expect that you would have to crank down on the spring preload to get the sag to 100MM, which would make the bike have very little static sag. (Won't sag much under it's own weight) I would expect that static sag less than an inch would indicate a spring that is too small so I'm curious why it's different.
Thanks
FT

 

[someday]

Springs, absolutely. The stock tires do suck too though.

 

[Robcolo]

QUOTE: "Given the kdx doesn't have rebound damping (well, in stock form),"
The KDX DOES have rebound damping - it's just not externally adjustable - and it may well be that it is insufficient and the front fork is rebounding too fast. Carver's correct that rapid rebound leads to understeer. The reason I'm suspecting the HIgh speed compression damping is that I feel EVERY little rock, ledge and bump [spiking] in the bars. I'm also going to shorten my stock springs to .37kg/mm & see how that goes as .35 is too soft even for my skinny little a. If rebound damping IS the problem, then it should worsen with the stiffer springs.

 

[Sage]

From reading the whole thing I come up with this much -

1) The stock tire will not work in mud & sand, you need a soft terrain tire, the stock dunlops are a hard pack tire

2) At 210#'s you need springs, depending on how fast you are and what type of terrain your riding in. the right spring is a .42-.44 kgmm but if you never get over 25 mph then a .38-.40 kgmm will feel better, I know Fredette will tell you anything over .39 will beat you to death but that's a very open ended statement that has way to many variables and if you go to the track like mentioned above then the .38’s will tuck all over the place.

 

[vandean]

Thanks for the help guys.I will buy a new front tire and order a set of .42 springs.Hope this helps.Rebound adj. would be nice to add but at what cost??? I'll check with race tech here.

 

[canyncarvr]

Given the kdx doesn't have rebound damping (well, in stock form)...

Hey!...I was THINKING 'adjustment'...external even!! I can't help it if my fingers weren't listening ;)

Fred:

CC
You wanna explain that one a little?

You bet.

Basically, it's backwards from what you might think. Too little free sag (less than 1/2 inch or so)=too light a spring, too much free sag (inch or more)=too heavy a spring.

This from Pro-Action's site (jeremy had the same fact on his site at one time. I didn't see it today.):

*Note: With the race sag set at 95 mm, the proper static sag should be between 15mm and 25mm (1/2" - 1").

If the static sag is less than 1/2" you need a stiffer spring. If it is more than 1" you need a lighter spring. Call us!

Take your '..if you are heavy..' (spring too light) situation.

If your sag is 110mm and you want 100mm, which way do you turn the adjuster? You make the spring LONGER (turn it 'out' if you will). The longer the spring is, the less free/static sag you'll have.

Exaggerate to make the point. Put in a spring that is 24" long. You won't have ANY free sag at all.

Take a 'spring too heavy' situation (you're too LIGHT...ha!!;) )

If your sag is 90mm and you want 100mm, you turn the adjuster to make the spring SHORTER (turn it 'in').

Use exaggeration again to make the point. Put in a spring that is 6" long. You'll have all sorts of free/static sag.

Therefore..as pro-action states..as 'tis so....verily it is written
:)

Please...no one take me to task for the 'short/long' thing. I realize the issue is NOT the length of the dang spring, but it DOES show what happens with a too heavy/too light spring. I think............;)

BTW:
http://www.pro-action.com/shock_tuning.htm

Cheers!!

 

[fatty_k]

Ok, I just need to straighten some things out here. I weigh 180lbs, do you guys recommend .44kg springs? I ride tight singletrack trails, which get very bumpy at times. Also, how do I set the sag in the forks? Is it hard to change fork oil and do I really need the special tools stated in the manual i.e, fork spring holder, fork piston rod puller? I am a total newbie to suspension, so bare with me. Thanks

 

[Fred T]

CC: Read what I said and compare it to your "Quote" from race tech - they match. Your original comment is not in agreement with your second post on that topic. Check it.
FT

 

[Matt90GT]

Personally it sounds like the front end is to stiff and your body position is wrong on the bike. If you are cornering be sure to have the elbows up and your body on the front of the bike.

Try this link for some help:

http://www.motocross.com/motoprof/moto/mcycle/others/sustable.html

Remember that you can also adjust the height of the forks in the tripple clamps to change the handling on the bike.

"If the front end rides low, turns too sharp, and/or tends to Head Shake, try a combination of lowering the front forks in the triple clamps and adjusting rear sag to 4 - 1/4 inches. "

You may want to try some of the links on this page for help in setting up the bike for yourself:

http://www.motocross.com/motoprof/moto/mcycle/suspen.html

 

[canyncarvr]

Well $&*%!!

THANKS!! I do so humbly and profusely apologize for the error.

I keep that straight by thinking, 'It's opposite of what you think'...and then I think oppositely...........

...well......let's leave it at Thank you for letting me know. :)

You are absolutely correct. The first post has been edited (and marked as such) for corrective purposes.

A mind is SUCH a terrible thing to waste. Use YOURS before many, multiple and numerous decades take it away!! ;)

fattyk:

At 180#, you won't likely be wanting more than .40.

No special tools needed for fork maint. You will need to fashion some sort of spring holder to access the piston rod jam nut to get the top cap off. You can use a wrench to do it, too. A piece of sheet metal with a slot cut in it works fine, too.

 

[marksilvia.cpa]

Go to the right source for your answers, Call Jeff Fredette. I weigh 220 and ride in terrain that varies from rocks, to sand, to tight single track trails, to whooped out dirt roads. I had Fredette revalve my front and rear, with new springs and Gold Valves in the front. It is perfect!!! The rea spring is stock. I use Pirelli MT-16's front and rear with 13# of air. Fredette can supply your springs and the right fork oil.

 

[Sage]

:| Pretty cool how 21# & 22# springs & 7wt oil at 100mm will fix the problems of the world because J.F. said so.

 

[fatty_k]

What are the stock springs? Is there any way of telling if they are stock springs in my forks right now? Some sort of markings? (Im not sure what the previous owner did.) Thanks.