Questions on re-sprung 220.

Perk · Dec 6, 2007

I just finished re-assembling my 02 220 after installing Fredette 40kg front springs. Used factory spacer and recommended amount of oil at 5wt. Have not ridden yet as my basement is not quite large enough for a test ride. However, after sitting on my bike after spring change and rocking back and forth heavily, the front end does not really seem to have changed over stock springs. Is this a ride to appreciate thing, or am I too heavy for springs? For what it's worth, I am about 205 with gear, "B" level hare scramble rider, no motocross.

Thanks as always,

Perk

blackduc98 · Dec 7, 2007

Perk said:
Fredette 40kg front springs ... factory spacer

Are fredette springs the same length as factory springs? If they are, then the factory spacer may give you the right amount of preload, but you should still check sag. If they are not the same length as factory springs, then factory spacer will probably result in incorrect amount of preload. In any case, check your sag and if you need to adjust it, you'll have to fabricate new spacers. You can use several different materials for that readily available at the hardware store, including copper pipe or PVC pipe (sorry I forgot what diameter, but it will be obvious once you measure the factory spacer).

Is this a ride to appreciate thing?

I honestly don't remember how it compared just sitting on the bike, but I do remember that the most obvious difference was amount of fork dive when using front brake. You'll notice it just putt-putting up and down your street.

Perk · Dec 7, 2007

Fredette springs are just a hair longer than stock. Maybe an eighth of an inch or so. Fredette did include a piece of PVC pipe with the order for making your own spacers, but I had no clue as to how much I was going to need, so I just went with stock for the time being. I figured that a much stiffer, slightly longer front spring would show me a huge improvement over stock, just by using the factory spacer. As it is now, I can get it to blow through about half of the travel just by sitting on the bike and rocking forward pretty hard.

As far as adjusting sag goes, that can only be done by inserting different length spacers, right? And is there any way to determine what size spacer you need other than trial and error?

blackduc98 · Dec 7, 2007

Perk said:
As it is now, I can get it to blow through about half of the travel just by sitting on the bike and rocking forward pretty hard.

I think that's OK.

As far as adjusting sag goes, that can only be done by inserting different length spacers, right?

Right.

And is there any way to determine what size spacer you need other than trial and error?

I think I can come up with an equation to calculate it, but you would have to know how much sprung weight is being applied to the spring. This you need to know for the case of bike-only (free sag) and bike+rider (race sag). I think you can figure out how much weight is being applied to the spring by putting a weight scale under the front wheel and recording the reading, From that reading you need to subtract unsprung weight. Wheel+tire+brake rotor+brake caliper are all part of unsprung weight, and so is lower part of the fork (which is hard to measure without disassembling the fork).

The bottom line is that it's a lot of work to obtain necessary inputs for the equation. So in practice it is easier just to go with trial-and-error. Start with a spacer that is intentionally too long, and gradually cut it down a little at a time.

I'll think about it some more and see if I can come up with an equation to determine "preload correction" without having to know all that unsprung weight business. But don't hold your breath.

blackduc98 · Dec 7, 2007

blackduc98 said:
The bottom line is that it's a lot of work to obtain necessary inputs for the equation. So in practice it is easier just to go with trial-and-error.

BTW, you may want to search the Suspension forum- maybe somebody already came up with a clever way to calculate required spacer length. Let me know if you find anything.

Perk · Dec 7, 2007

I have done a good bit of searching prior to starting this task, but never really found what I was looking for. Did find a lot of other info that helped me out a lot with the actual "getting it done" aspect. If I get into that trial and error part of the spacer, I'm gonna need to come up with some kind of home made tool to help me get that spring compressed enough so that I can get that top cap on a little easier. Doing that by myself the first go around provided for some colorful language in the basement.

blackduc98 · Dec 7, 2007

Perk said:
I'm gonna need to come up with some kind of home made tool to help me get that spring compressed enough so that I can get that top cap on a little easier. Doing that by myself the first go around provided for some colorful language in the basement.

That's an easy problem to address. I made a spring holder tool which looks similar to what you see in the kdx200 manual. Take a small piece of steel or aluminum, about 3" x 3" by 1/16 thick. Cut a U-shaped slot from the middle of one of the 4 sides to the center. Make the width of the slot just a little over 10mm. So basically it's just a flat plate with a long narrow U-shape cutout.

You will slip this holder under the rod nut as you compress the spring with your other hand. One quick jerk movement is all you need to slip the holder into place. Once the holder is in place, the spring spacer will be pressing into the holder instead of the fork cap. Now you can hold the rod nut with a wrench while you unscrew the fork cap without the drama of fork cap flying across your basement.

Perk · Dec 8, 2007

What you described is exactly what I was picturing, just a flat plate with a U cut. Great minds think alike.

hart125 · Dec 10, 2007

dude,, dont' worry about it.. the frp springs are just the right height if you use the stock spacers. What your feeling in the garage proves nothing. you will notice a lot difference when you ride it. I felt the same way when I sat on mine and pushed down but i did notice with the .38's the front sag was less. thats all you should notice while just sitting on it.

Perk · Dec 10, 2007

Sounds good to me. I'll just go ahead and ride and see what I feel. If I'm happy, then my work is done.

glad2ride · Dec 20, 2007

At 205 in gear, .40's are a little soft, in my opinion. If you are shotting for 25% sag when on the bike, I think it will be a bit off.

On the fork springs, around 10mm of preload is normal, not the 28-ish mm (or is it 38-ish mm?) of stock preload.

A correct rate (stiffer than .40) spring with 10mm of preload will be more plush initially and keep the front end higher than softer springs with more preload.

Perk · Dec 21, 2007

Well with the forks installed, I am right at 50mm of race sag on the bike, but I have not ridden it yet. I assume after a few rides they will settle and I will see a bit more sag. Is that correct?

glad2ride · Dec 29, 2007

You can keep playing with spacer length until it gets to exactly 25.00% of travel, but it doesn't mean it will ride properly, or perhaps perform as well as it should.

If you have time and are interested, do an A-B comparison of the stock amount of preload vs. 10mm and see which one you like better.

Jeff Sexton · Jan 11, 2008

Actually, 70-75 mm of race sag on the forks is what I shoot for on the KDX. I check in at 230 and use .42 springs from Race Tech. This set up works real well for me using the stock spacers. This made a huge difference in how the bike handles. If you like the stiffer front end (and you will), you'll really like the shim stack mod. Together, they make the KDX a real fun ride on tight nasty trails. Enjoy!

Jeff Sexton · Jan 11, 2008

Forgot to ask...

You said you're running the recommended oil level. Fredette's recommendation or the Kawasaki manual? For what it's worth, I've been real happy with Mobil 1 Synthetic ATF in my forks at 80 mm from the top of the tube with spring and spacer removed. The ATF is a little heavier than 5W fork oil. It may not work for everyone, but it works real well for me.

Perk · Jan 12, 2008

Well, I finally got to go riding last Sunday to check it out. The front end still felt as plush as ever on small stuff, but soaked up bigger hits a lot better. Also the bike seemed to be better balanced front to rear. I was expecting with the heavier spring that I would "feel" a lot more of the smaller hits, but that never happened.

glad2ride · Jan 15, 2008

For even more initial plushness, go with a modern amount of preload - about 10mm and not the stock amount.

The stock amount of preload is a poor choice for stock or aftermarket springs.

RickSA · Feb 18, 2008

I found a post the other day which i've been desperately been looking for again about cutting the stock fork springs and increasing the spacer size to get a harder spring. The guy that posted it needed to go to a .42 so many people said not to as there was a risk of bottoming out earlier and loosing travel. MXtech recommend i go to a .38.

Has anybody tried this for a small amount like this? Is there still a risk of bottoming out too early?
My front end is not too bad at lower speeds but at higher speeds the bars shake far too much over small bumps, throughout the whole range of the clicker! Any suggestions there?

Thanks for all the help guys! ;)

Questions on re-sprung 220.

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