Fork Springs/Suspension Tuning

[EBOD]

Just finished my maiden voyage on a new KDX 220. I rode it completely stock. I am 6'0" and about 200 LBs. w/out gear and I ride trails for fun (no racing). I don't ride super-tight wooded trails, but I'm not riding out in the wide open desert either.

The bike was great. The only things I noticed are: (i) the bike needs a bit more top end power (to be fixed w/ FMF rev pipe); and (ii) the bike really dove a lot when braking.

People say that heavier riders need to change the front springs. I assume that that is what I need to do. To that end, I have a few questions:

1) Should I try to fix the problem by changing the compression damping, before getting new springs? If springs are inevitable, I guess I should get them now.

2) In the future, I may do more extensive fork work (e.g., revalve). I'm not ready to do that yet. Is there any problem with getting the springs first and then (hopefully a lot later) doing fork tuning work?

3) If I don't do anything to my rear spring, will the bike be out of balance?

4) My mechanic says it will take about an hour of labor to change the springs, does that sound about right? I'm not mechanically gifted so I don't want to mess with my brand new bike myself.

5) Does any one have good suggestions as to what type of spring may be best for me?

Any thoughts would be appreciated. Thanks!!

 

[MADisher]

Yes, get springs, do a search for fork springs and you'll find lots of responses.

You have a couple options: Call Jeff Fredette or Sage and they can pick the right aftermarket springs for your weight. @ 200lbs I think they are .45kg but I could be wrong. Also there are Honda springs that are supposed to be better, stronger longer needing less pre-load. I'm going to try those next myself in the spring (no pun inteneded).

lastly an hour for a gifted mechanic would be about right. For the average Joe changing the springs, and removing the forks and changing the oil is a 1-2 hour job or 2-3 beer job depending on your time keeping system.

There are photos and a short tutorial on how to do this on my website. It's easier than you think. I was a bit hesitant at first but didn't/couldn't afford to pay someone to do it.

-MD

 

[OLD-N-SLOW]

Everything you said is right. Do the springs , 1 hour of shop labor sounds fine. The heavier spring will put the bike in balance, a better match for the rear shock spring which by the way is just about right for you.
I weigh 225#s no gear and bought .44 kg and mostly trail ride and I think if I had it to do over I would go with .42kg springs. Keep in mind you wont find a slower rider than me! A faster rider might find them just right. To me .40-.42 would be good for you.
In anycase the heavier spring will make a great improvement.
Also do a search on the air box lid mod or removal.
Steve

 

[Sage]

How fast are you & how do you like your suspension to feel? soft, med or hard?

 

[canyncarvr]

a one, and-a two, and-a three...

1. New springs are inevitable. Get them now.

2. Putting in new springs now will have no effect on being able to do a revalve later. Might duplicate some labor expense.

3. The stock shock spring (5.0kg/mm) should be fine.

4. You don't need to be mechanically 'gifted' to change your springs. Consider that the oil in the forks needs to be changed a couple times a year, which pretty much involves the same work as changing the springs. You going to pay someone to do that, too?

If not 'gifted' means you don't consider torque values when assembling something...or if you take apart a 1,2,3 piece and don't know if it goes back together 3,1,2 or 2,3,1..then pay the man.

Who's doing your carb tuning?? That takes as much 'gift' ...and that's ALways something that needs tweaking.

Line up a couple of brew-skis, do some research on springs and stuff on this site (like check out MAD's site) and give it a go!

Heck..even if you take it to someone to be done, you can STILL enjoy the brews!!

Oh..re: top-end power. A rev pipe doesn't so much 'add to' the top end as it shifts the power band 'up' within the existing range. The 220 is short-breathed in large part due to its 33mm carb. Boring it to 36mm costs less than a pipe...although you need that, TOO! ;)

 

[old trapper]

I have a question, plus I am a little confused now.

I just got a service manual on the KDX, the manual shows .70kg/mm fork springs as standard. It also shows optional springs from kawasaki, .72kg/mm
and .74kg/mm.

So the question is has anyone tried any of these optional springs?

The confusion is the spring rates don't match any of the rates I have seen
posted.

 

[MADisher]

I don't know anyone that has gone back to kawi and gotten thier springs. Probably like thier $32.00 lightbulbs they have probably priced themselves out of the market. I would also venture to guess that other aftermarket springs simply work out better for what ever reason (better quality and/or availability). I can't explain the differences in the markings/specifications. I know i put in .38's of what ever that is and really needed to be at .42 or .45

good luck

 

[canyncarvr]

If it says .70kg/mm springs...it's certainly wrong.

Mostly you'll hear kg/mm...and numbers of .40, .42 and such. Maybe lb/in. Then you'll be dealing with numbers of 21, 22 and such.

Ha! A KDX with .70 springs. First time you hit anything you'd blow out the tire, bend the rim and THEN break both your arms!

 

[fishhead]

heavier springs with less preload tend to react faster to bumps than light springs with lots of preload -just the ticket for trail riding. Re- valving is a great option as the stock valving in the forks is harsh over the square edge bumps. you might want to run your fork oil at 130mm orm 135 mm using #1 (light ) fork oil.

You will find a couple different schools of thought
1) light springs with lots of preload and a high oil level to prevent bottoming
2) stiff springs with 6 to 10mm preload and low fork oil to maintain constant rate through the stroke of the fork.

I found #2 to work the best for me in tight woods riding, a little wallowing didn't bother me in g-outs as much as fork deflection on square edge bumps (wet roots and rocks) at 190 plus gear I am running 042's w/ 8mm preload and silkolene 5 at 130mm. If you are on the chart for your weight and spring selection and it still seems harsh I would back off the clicker a couple clicks If you can't get it there go for the re-valve. you might look at the spring rate for the rear shock I run a 5.2 stock is 5.0