98 kdx200 with 03 yz250 forks.

Questions and comments about converting to beefier forks..
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Steelerfan820
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98 kdx200 with 03 yz250 forks.

Post by Steelerfan820 »

I recently purchased a 1998 kdx200 with a set of 2003 yz250 forks. Bike feels way outta balance. And washes out in corners. Want to get this thing balanced and have no idea what kg the springs are. Im around 190-195. I believe the rear suspension is bone stock. But the front who knows. Anyway, does anyone know what would be the spring rates for my weight. Tried using racetechs calculator but having to put in two different bikes is confusing as yz specs doesnt take into consideration kdxs weight.
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Re: 98 kdx200 with 03 yz250 forks.

Post by KDXGarage »

Check to see if it looks balanced while on a workstand. The forks might be taller than the stock forks.

The springs need to be measured to see their rate.

You might need a 5.2 spring in the rear instead of the stock 5.0 Kg / mm. Are you 190 - 195 with all your gear or that is just you?

When using a spring calculator, select the bike, not the forks.
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Re: 98 kdx200 with 03 yz250 forks.

Post by bufftester »

Just use the racetech calculator for the bike and then order the proper spring weight for the fork. i.e.: if the calculator says .42 kg springs for the KDX and your info, then order .42kg springs for the proper year model YZ. As KDX said, you will want to check the rear spring as well. (and do your riding weight with ALL your gear/water/tools/etc you normally ride with.) Then check the fork length against the KDX stock fork lengths. As KDX mentions, generally the USD forks are longer and if they are, and not lowered in the clamps, then your rake and trail change which affects the geometry. And finally make sure your sag numbers are good. That will cross check your spring rates for you.
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Re: 98 kdx200 with 03 yz250 forks.

Post by doakley »

When I switched to 2001 KX250 forks, I had to raise them in the clamps to stop the front end wash out also, FWIW.
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Re: 98 kdx200 with 03 yz250 forks.

Post by SS109 »

doakley wrote: 05:32 pm Jan 07 2022 When I switched to 2001 KX250 forks, I had to raise them in the clamps to stop the front end wash out also, FWIW.
Same here on my '06 KX250f forks.

You either have to raise them high enough in the clamps (the cheap hack way) to get within the stock geometry or have them internally shortened (proper way) to do the same. Now, some people can get away with the hack way and others can't. It all depend on your setup and riding style because if you bottom out the tire can potentially hit the lower triple, lock the front tire up, and eject you over the bars. I am running one fork spring size stiffer than what I normally run, .40's instead of .38's, to keep it from happening but I still get some fender rubbing at times. So, be careful with what you do! :mrgreen:
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Re: 98 kdx200 with 03 yz250 forks.

Post by doakley »

I think I raised them 1/2 ". I've never hit the fender. And the "hack" that helped me set this up makes his living custom tuning suspension at the pro level.
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Re: 98 kdx200 with 03 yz250 forks.

Post by KDXGarage »

He's a pro. That's why he didn't say a whole inch. :-)
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Re: 98 kdx200 with 03 yz250 forks.

Post by SS109 »

doakley wrote: 04:39 pm Jan 14 2022 I think I raised them 1/2 ". I've never hit the fender. And the "hack" that helped me set this up makes his living custom tuning suspension at the pro level.
I wasn't trying to insult anyone with my "hack" comment because, as I said, I did it too. However, even pros can make mistakes. I highly doubt that a .5" is nearly enough but admit I don't know the length of your current forks. Mine took over an inch to get it near factory spec. To get them matched up you need to measure the fully extended stock forks from the top down to the axle center line, do the same on the YZ forks, and then slide the YZ forks up in the clamps what the difference is just to start with. That will set your minimum height of the forks in the clamps and a lot of people find they still need another 5mm or so to get the handling right.
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Re: 98 kdx200 with 03 yz250 forks.

Post by KDXGarage »

Don't forget to run the correct rate spring on the shock and set the sag properly. A too soft rear end will contribute to the chopper like handling.
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