Fork Springs

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patreilly
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Fork Springs

Post by patreilly »

Thanks guys. I made the 27mm welded nut inner tube holder and took one leg of my forks apart. Worked great.
Now I have another question. My manual says the serviceable spring length (stock springs) is 457.5mm to 448mm long. Mine are 470mm. they must be after market. The spring wire size is 4.41mm dia.. I suppose I should bite the bullet and buy a new set of springs. Any way to measure these springs, or should I bite that bullet and hunt for the 38 springs recommended by the Race Tech schedule, the lightest spring they supply is a 42. What do these numbers represent?
I am calling Race Tech tomorrow to ask them to clarify their installation instructions. There is a valve on the bottom of the dampener rod and one on the top of the bottom plug. I think I put their valve on the plug, but what about the one on the dampener rod. I suppose it stays as the instructions say nothing about it.
Any recommendations on this valve installation and fork rebuild is appreciated.
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Re: Fork Springs

Post by KDXGarage »

OK. Which KDX is it?

What is your weight in full riding gear with all spare tools, water backpack, etc. ?

I doubt someone put in aftermarket springs that were softer.

The springs can be checked by using a dowel, weightlifting weights and a measuring stick. Measuring how far they compress per inch will lottery you know the rate. The difference between one to two and two to three are what you need to know. Zero to one is not accurate enough.

A Race Tech Gold Valve goes on the bottom part, which is the compression adjuster assembly. The valve on the end of the damper rod is the rebound.
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patreilly
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Re: Fork Springs

Post by patreilly »

Jason, Thanks for the info. Sorry, I meant to list the bike, it's a 2002 220. I did use the Race Tech schedule that said I needed the 38 spring. The lightest spring they offer is a 42. Thanks for the weight method explanation of checking the springs. Is the # ,such as the 38, the weight to compress by 1 inch? Higher #'s are stiffer springs so the # can't be the amount compressed. Also, how about the springs being longer than the service length range?
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Re: Fork Springs

Post by 6 Riders »

Hmm, .38 springs are a little light weight. What is your weight and riding style? How fast do you like to go and etc.
newbbewb wrote:^what he said.
masterblaster wrote:Man 6 riders you rock.
*side note...I'm drunk, so try to read what I'm trying to say, instead of what I actually type
patreilly
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Re: Fork Springs

Post by patreilly »

Yes the .38 spring would be light. The statistics I used on the Race Tech site to determine the correct weight spring were; weight 175#, 5'8'' tall, over 45 years old (way over, but that's the bracket they use), Senior B enduro rider, ride dual sport and enduro (hope to ride a couple more enduros anyway).
The best woods bike, suspension wise, I ever owned was a 92 Yamaha WR200, brought in the country 1 year only. The stock suspension was extremely plush, soft. I want as plush a suspension as I can get. I owned a 200 KDX 220 with stock suspension. It also was good but the Yami was better. I never had the KDX set up spacifically for me, ran it stock.
I also owned a KTM xcw200. The bike was very powerful and fast. It was 5 years old with 12 hours on it when I purchased it. I only played with the clickers on the suspension some. I did not like the suspension on the bike one bit. I really can't fault the bike, might even still have it if I would have had the suspension dialed in. I never had the suspension tuned by someone that knew what they were doing. I could not loft the front end with out giving it so much throttle that, instead of lofting the front end, it would loose traction.
What does the .38 signify on the spring designation?
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Re: Fork Springs

Post by 6 Riders »

Well....If you want the suspension tuned right, take the bike to a suspension shop, let them work their magic. I was originally going to go with .38 springs, but then I decided to have the forks done by a suspension guy. He recommended .41s and some "massaging" of the forks. At 160#, 45 YO B rider, I wouldn't go softer. It seems to me that .41 springs really soak up the small vibrations and let me ride the slow technical stuff with ease. But again, I had my forks completely rebuilt by a pro. In fact, I've had a set of KDX forks done as well as RM forks that I have on my other KDX done by the same guy. Both forks run .41 springs with (of course) some tuning.
newbbewb wrote:^what he said.
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*side note...I'm drunk, so try to read what I'm trying to say, instead of what I actually type
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Re: Fork Springs

Post by KDXGarage »

.38 means .38 Kg of force required to compress the spring one millimeter. 25.4 mm in an inch. 2.201 pounds per Kilogram. Springs may also be rated at pounds per inch.

Just go for around 4 mm of preload. The springs being a different length is no problem. Just cut the current spacers to make it to where it has 4 mm of preload. One can also use PVC pipe cut to the correct length.

In stock form, the fork springs have a ton of preload, which is a real old school way of looking at things. With stiffer springs and very little preload, they will be more cushy at the start than the stock springs and high preload. The benefit is when it gets to a rougher bump, the stiffer springs better handle it to keep the bike's weight and rider weight supported.
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Re: Fork Springs

Post by KDXGarage »

If you are 175 in your birthday suit, .38 is not going to cut it.
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Re: Fork Springs

Post by patreilly »

WOW, thanks again guys. I'm still working on right springs and appreciate the spring rate info and opinion. I'm 175# with gear give or take a couple #. FRP site says .38mm/kg, Race tech site said .38mm/kg. I need to build a jig to test my springs. I will report my findings. Thanks for the kg to # factor, saved me looking it up. Thanks for the 4mm preload figure. I'll call that a1/4 of an inch. I was wondering about using PVC for a spacer, but wasn't thinking about changing length to correct preload. Glad to hear someone else has used PVC and now I can adjust preload.
After a significant amount of time deciphering the instruction sheet and a call to Race Tech, I completed the assembly of the 1st valve. Then I spent only a few minutes disassembling, cleaning and assembling the 2nd one.
One more question, what tool do you use to remove the dust seal. I forgot there was a retaining clip under that seal and slammed the inner tube until 2/3rds of that retaining clip poped out and was sticking out where I could see it.
Hate to say it guys, but with the info you guys have given me on this post and the Race Tech info, I am confident the forks will be as good as they can get if I just get the right spring.
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Re: Fork Springs

Post by KDXGarage »

Did you change the bushings? Game is on, but I would REALLY look at those.
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Re: Fork Springs

Post by patreilly »

Jason, Thanks for asking. I ordered a new set. The old ones look good, but no sense tearing down and not replacing.
I still want to know the best method for removing the dust seals to get access to the seal retainer clip?
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Re: Fork Springs

Post by doakley »

As long as you are in the forks, check out the thread on the "shim stack" mod. Easy to do yourself and really helps with the sharp edged bumps, roots, etc. softens the initial impact. Awfully glad I did mine. Best thing is, if you don't like it, just put it back stock.
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Re: Fork Springs

Post by KDXGarage »

Flat blade screwdriver to pry out the dust seals.

doakley, I think he has Gold Valves
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Re: Fork Springs

Post by patreilly »

Doakley, Yes, Jason is right I have the Race Tech Gold valves, matter of fact with what it took to learn how to install them, I feel like an expert . But, if you want to explain what " the thread on the shim stack mod" is, I'm always trying to learn. I think I will be restoring a few more KDX's if I can find the later ones.
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Re: Fork Springs

Post by patreilly »

Hope your still following this post. I can't figure how I previously started a new post.
I fabricated my spring test jig and tested a fork spring. I can't seem to make the math work. Tested with 1 1/2" preload as suggested. Used 5# which would be 2.2717 kg using the 2.201 # per kg.
5# weight collapsed the spring 67.5 mm.
divided 2.2717 by 67.5 = .03365 kg/mm of travel. What am I doing wrong?
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Re: Fork Springs

Post by KDXGarage »

Read the other thread for a decent answer. Thanks.
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