KDX Suspension Upgrades

[Jimbokdx]

OK, I have a 94 KDX 200. I have the FMF Fatty pipe and silencer, airbox mod, boysen reed valves, 12 tooth front sprocket, and heavier fork springs (I believe they are .40).

Other than the fork springs, my suspension is stock. I am in a delima... do I continue to upgrade, or do I buy a new bike?

Is the RB Carb mod worth it for th 200? It is not much of a bore job, but does it make that much difference?

If I upgrade the suspension, what should I do and how much will it cost me? I am 6', 180# and I ride mostly in the desert (not high speed, mostly hills, whoops and rocks).

Thanks for any input.

Jimbo

 

[limitless]

mx-tech valves are pretty good from what I hear and make a substantial improvement in stearing.... as for the carb mod I dont think it would make that much of a difference & EG says that he thinks that boreing a carb works evils on the venturi some way (thats why he doesnt do them)

I would go back to the stock 13 tooth on the front sprocket and go up a couple on the rear (its more expensive but changing the front can have some ill effects) also If your looking for more power get in contact with eric gorr about a port job! (I've heard that having it ported gives you more power than an fmf pipe, so if you combine the 2 you cant go wrong)

good luck, keep us updated....
Tom

 

[limitless]

mx-tech valves cost around 600$ (I think?) for front and back and I'm not sure about EG porting (I'm guessing around 300$) but should be totaly worth it

 

[Rich Rohrich]

Eric Gorr's porting is $150 for the KDX

 

[limitless]

was I in the ball park on the mx-tech valves?

 

[Fred T]

Originally posted by limitless
was I in the ball park on the mx-tech valves?

I think he charges 225 per end plus seals, bushes, and shipping so you're close but maybe a little high unless he gets some springs too.

 

[toalco-kdx]

Poste by Limitless:
"...EG says that he thinks that boreing a carb works evils on the venturi some way..."

Whats the venturi and what does the mod do to the bike thats bad? I was thinking about getting the RB carb mod, so if you could tell me what it does bad that will help me alot.
I think that you can get Race Tech suspension for about $500(CAN$) so that works out less that MX-Tech, I think. But does MX-Tech offer higher quality suspension that Race Tech?

 

[40]

limitless:

what are the ill effects with running a 12 tooth front sprocket??

 

[Jimbokdx]

I have always run 12T front sprockets on my KDX, no problems yet. The only problem is that I am stupid when it comes to suspension upgrades. I really don't know what to do first.

Jimbo

 

[powercart]

Jimbo, my kdx is in the shop right now getting a new top end, pipe/silencer, boysen reeds, so on. Mine is also a 1994, does the ugrades make a big diff from stock?? Sorry to change the topic....

 

[Jimbokdx]

Powercart,

With the upgrades you are talking about, you won't recognize it as being the same bike. The pipe and reeds transform the engine. Make sure you do the airbox mod.

Have you done any suspension mods?

Jimbo

 

[JasonWho]

---

 

[Robcolo]

The smaller the sprocket, the more load there is per tooth on both sprocket and chain. You simply wear out your drive train faster with smaller sprockets.
It takes a lot of money to upgrade the Kdx suspension and I don't think those estimates included replacing the rebound valves -- which you need to do if you install stiffer springs[actually you need to replace them even with stock springs] The suspension is horribly "confused" and requires many changes to "get it right". When you finally make all of the changes, you unfortunatelyl have a very expensive 1980s technology forks & shock. Oh, you'll also need to pop $300 - $600 for a steering stabilizer if you want to ride in the top 3 gears.

 

[sledman]

Originally posted by Robcolo
The smaller the sprocket, the more load there is per tooth on both sprocket and chain. You simply wear out your drive train faster with smaller sprockets.
It takes a lot of money to upgrade the Kdx suspension and I don't think those estimates included replacing the rebound valves -- which you need to do if you install stiffer springs[actually you need to replace them even with stock springs] The suspension is horribly "confused" and requires many changes to "get it right". When you finally make all of the changes, you unfortunatelyl have a very expensive 1980s technology forks & shock. Oh, you'll also need to pop $300 - $600 for a steering stabilizer if you want to ride in the top 3 gears.

So your suggestion is.................

 

[powercart]

Jimbokdx, All im getting done is race tech springs in the front, im glad to head that my bike will be faster, its costing me 1500 bux to get it all done.

 

[limitless]

toloco - "Personally I don't bore carbs because I think that it changes some critical ratios inside the venturi." - Eric gorr
Though a lot of people do bore the carb and like it, I would rather get a torque pipe & have it ported for the mid-top range (the best of both worlds!).


40 - Robcola is on the ball, it wears "stuff" out quicker.

Yeah I think the 600$ quote for mxtech valves was including fork & shock springs... Everyone has to at least change one(well, if there going to set them up correctly).

 

[Jimbokdx]

Wow... I guess suspension upgrades are going to be really expensive. Do I really need to do it all at once? Where does a guy on a budget put his money first?

Jimbo

 

[limitless]

how much are you looking to spend?....
1. I would put a 13 tooth front sproket on ($20?) and a 50 rear($60, if you dont like the gearing with a 13).
2. I would go for the mx-tech valves or race tech ($600 front & back if you install)
3. Set the race sag and get the susp. tuned real good. (time)
4. Scotts stabilizer kit ($600 or 450 without the handlebars & tripple clamp)

Power!
1. Uni-air filter ($22)
2. Eric gore porting ($150, I wouldnt mess with the carb, just jet it properly)

I'd get the susp. done before the porting & stabilizer, but do the rest before the susp.

I dont know what kind of riding/racing you're doing, but the kdx can be a mean green woods machine..... Not much of a motocrosser though.

 

[Robcolo]

Is there a 7 - 11 in the neighborhood that you could rob ? The KDX BOTH understeers and oversteers ! The oversteer is due to the steep steering head angle and is then exaggerated by the soft front spring so increasing the spring rate will help [just a bit]. This trait is what makes the KDX such a great tight woods bike and if you try to correct it by the usual means it won't be a great woods bike anymore. I think adding a steering dampener is the best way to tame the oversteer at higher speeds and still retain the precise steering in slower going The bike also understeers[washes out] on fast corners making it really scary at times. This problem is most likely caused by improper internal dampening. The stock high speed compression dampening is way too stiff --causing the front tire to bounce from bump to bump --beating your arms to a pulp and allowing the front end to just bounce right off of the trail if it goes any direction other than straight. Installing Gold Valves has cured this one for me -- This is your # 1 priority When you install stiffer springs, you overpower the already too fast rebound valve and too rapid rebound contributes to understeer. I took 3 shims from each of my discarded compression valves and added them to the rebound stack. It seems to have helped. If your bike is more than 1 or 2 years old [yes] there is a fiber bushing thats worn out and allows most of the oil to simply avoid passing through the rebound valves. It's located on the top of the cartridge where the central rebound valve stem passes through and should be replaced. The rear shock on mine hydraulic locks when encountering certain square edged bumps -all of a sudden the rear end is 3 ft out to the side. Again, the high speed compression is the culprit and must be reduced. The "clickers" only affect LOW Speed Compression. You can either install another Gold Valve here or remove a couple of shims from the high speed stack. Race-Tech sends a nice booklet with the GVs explaining all of this stuff.

 

[kristyh9]

Any oppinions on rear tyres .I ran a 100 /100 for years on my KDX but found the rear end was all over the place in heavy braking ecspecially on big down hills changed to 110/100 .Its so much better .The rear end feels so much more stable.What do you thiink fellas. Paul

 

[kristyh9]

Sorry Jimbo .Im new at this forum stuff .I think i stuffed up.Anyway any oppinions on tyres.

 

[acutemp]

Jimbokdx,
Before you get frustrated about the cost of new suspension I would take a good look at what your needs are. Are you bottoming out the suspension as it is? If you do have .40's in front you should be pretty close so new spring's shouldn't be needed. Next set your sag in the back and see how close the rear spring is. If it is correct then next I would change the oil in the forks and shock. New oil can make a big difference if it hasn't been changed for awhile. Work with the clicker's front and rear and see if you can find a setting that works for you. If you are still not satisfied then a revalve might be in order. If you have some tools installing the gold valves is pretty simple. There is a great how to article on installing the gold vales in the forks on the planetklx website that you might want to check out. They klx's inverted forks are very similar to your 94's forks and the install procedure is the same. I have installed several sets myself if you need help also. MX Tech used to sell revalve kits also but I don't see them on their website, I would check with them on this as they make very high quality parts. Good luck with your upgrades.
limitless,
Boring the 33mm 220 carb is a bit different situation than most other carb's. The small body pwk's are designed as 35mm carbs and on the 33mm version the bore is offset to the bottom of the carb body so that the jet stand fits into the carb bore at the same height as on the 35mm. When boring the 33mm carb most of the metal is removed from the top and sides but not the bottom so the jet stand is at the same height as before the boring. If anything I would think that boring a 33mm carb to 35mm would be bringing it closer to the original design of the carb.
--Dan