Spring Rate Question

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crash
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Spring Rate Question

Post by crash »

Hi Guys,

building my retro racer here its a 96 200, ive got the top end at Fredett's, about $1500 work shiny new goodies in a box, and the suspension with our builder. The KDX is a little older that what hes used to doing so i was going to see what other would recommend spring wise. Im 195lb, race AA, mostly Gnarly single track, but it will get a good beating down south in the sand hills during the winters where its knee deep sand whoops and super tight single track, so the bike is going to get a good mix. all my race bikes, and my dual sport and adv bikes i usually way over spring and under valve for woods, but this KDX is a new world for me. any recommendations would be appreciated

thanks
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bufftester
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Re: Spring Rate Question

Post by bufftester »

Aftermarket, Racetech is one of the few (maybe only at this point) non-OEM options and they have a pretty good calculator on their site. The OEM front only has preload and compression damping to play with, while the rear has both compression and rebound. The rear works pretty well when sprung properly, the front will run into it's limits pretty quickly when ridden hard. Unless you're trying to comply with some vintage regulations I would look at replacing the front forks with something a little newer and from the KX side of the house, spring them for your weight, and probably drop money on valving work. If sticking to the stock bouncers then the Gold Valves are a good choice to extend the forks capabilities a bit.
crash
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Re: Spring Rate Question

Post by crash »

Thanks for the input, I'm intentionally sticking with the original forks I like to do not modify what is on the bike. my suspension builder is re vavling them, which should take care of them being a pogo stick and super soft. I tried fredette's spring reccomendation but it was not enough spring, I'll take a look at race tech to see what they say spring wise. We were talking about having some custom spring made so I can get the front end to ride in the top of the stroke where I like it but if I can get something out of the box id my ch rather go that way
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Re: Spring Rate Question

Post by KDXGarage »

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

Being AA level and riding the stock KDX forks is not going to be a good match. :-)

Are you opposed to the Race Tech Gold valves?
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crash
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Re: Spring Rate Question

Post by crash »

210-212 depending on the day, im not against the Gold valves i have a few of them laying around the house from previous bikes i've just always been able to get better results from a custom builder who knows and rides with me such as this guy and he stands behind it if its not 100% he tears it back apart and re-valves it again and again and will do so until is perfect for free. i was just curious on spring rate for the forks wondering if anyone had intentionally over sprung a KDX and what results they may have found by doing so.

i actually did a similar type build on a DR650 believe it or not and it turned out amazing, 55,000 miles and it has raced motocross, enduro, hare scramble, Rally you name it. its sprung for 300lbs running 94mm of sag on a +2mm shock shaft in a cogent shock on there rear and 30mm pre load spacers up front on Cogent DDC's in the OEM forks. My concern with doing that to the KDX is with it being such a light nimble machine im afraid if I apply that same strategy and way over spring it will cause the bike to become super twitchy at high speed and really want to tuck on flat corners and turn out of a long deep rut since it so much lighter.
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Re: Spring Rate Question

Post by KDXGarage »

I'll just throw this out there since it sounds like you are used to more modern (1989 and newer) style forks. The KDX forks have a reverse bending shim design. There is no midvalve. It is equivalent to a 1988 KX. It does not have the standard compression and rebound pistons with stacks of shims to rearrange and add to / take away from. As such, there is extremely little revalving that can be done.

I have never intentionally oversprung the front.

Good luck with it.
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crash
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Re: Spring Rate Question

Post by crash »

hey thanks for the input i appreciate any advice i can get, we have something custom in the works for the mid-valve issue. once its tested and if he gives me permission to share ill gladly pass it along, the older Kx100 and 80 forks had the same issue and internal workings pre 03 i believe it was and he is working on adapting some technology he used to fix those to the internals of my KDX forks. i went for it on trying the over spring method we used on the DR, ill report back my findings good or bad. im not expecting to make these forks work like whats on my new KTM's and Kawi's, just looking to see how good they can get and have some fun experimenting along way.
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Re: Spring Rate Question

Post by KDXGarage »

Look on www.racingsuspensionproducts.com.

They have a kit that looks nice.
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Re: Spring Rate Question

Post by KDXGarage »

Thank you for participating on kdxrider.net. :bravo:
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crash
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Re: Spring Rate Question

Post by crash »

Thanks for that, that is what im looking for. Oddly enough ill be in Colechester CT tomorrow where that company is located. ill buy a set and give them a try
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Re: Spring Rate Question

Post by KDXGarage »

Cool. Let us know how it turns out.
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crash
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Re: Spring Rate Question

Post by crash »

so the company was closed while i was in CT, i tried calling but no answer so i left a message. I guess ill just place an order on their website or wait for their call back...........
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Re: Spring Rate Question

Post by SS109 »

Late to the conversation but my .02.

As a AA, I think you're not going to like the forks unless you keep the speed down. Even if the valving/springs are perfect the forks will still flex a lot. I did the fork swap on my '90 and loved it. However, when I bought my '98 I decided to keep the stock forks because they work so well in the technical/rough stuff. Once I got the bike dialed in my speed increased to the point that the forks almost got me seriously hurt more than a few times. So, I did the fork conversion again and never looked back. Of course, you AA/A guys can ride stuff that will kill this lowly B racer so take my input for what it's worth.

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