Fork spring rates KTM RFS

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Apr 29, 2001
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#1
I ride an '01 KTM 520 EXC. The stock fork springs were too soft to set the proper sag without 1.5" spacers. I bought .48 springs and have only the stock spacers in with the proper race sag now (95mm). My problem seems to be slow speed rocks. With the stock springs and 1.5" of preload the slow speed softball size rocks were not noticable. With the .48s the rocks kill me. The bike seems to deflect off rather than soak up now. I have set comp from mid to full soft and played with rebound, but nothing seems to help.

My question is what are the consequences of running the softer spring preloaded? The bike does dive a lot more with the softer springs :( .

Any other suggestions would also be appriciated.

BTW weight 300lb no gear, 8.8 spring in back.
 
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Mar 21, 2000
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#2
Not sure about the front springs, they seem to match up considering your weight, but you are way undersprung on the rear. I would think a 10.0+ would be more appropriate. I am 210 lbs no gear and I am using a 9.0 and I have it preloaded pretty good to get proper sag. The static sag in the front to me does not seem to be a critical issue on this bike. I have .45's in the front with the stock spacers. This is still a fairly soft setup but with the oil height run at 120mm (max), it has good enough bottoming resistance for my application.
The stock fork springs on this bike are .42. You made a big jump with the .48's. I would try a set of .45's or 46's before I started trying to fit preload spacers in the forks.
 
Last edited:

DanS

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#3
If the 48's feel too stiff try switching one with a stock spring. That will give you a rate somewhere in the middle of the two. As for the rear, I go 205 w/gear and run a 9.0 on my '99 300exc. The 8.8 would be pretty soft for your weight. If both ends are not balanced it make things feel way off. The thing I found about going to a straight rate spring with the PDS shock is that it needs to be revalved to work right. Give MX-Tech a call. They helped me out with my bike and the suspension works great now.
 
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#4
Maybe the back was a 9.8, I'll have to check my invoice. The back was re-valved a few weeks ago when I broke the spring adjuster ring. I am pretty happy with it, although it is not as good as my 98 YZ 400 was. I'll try the .42 in one fork and see how it goes.

Thanks for the info.
 
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#5
How much preload are you running with the .48's? Try running 3 or 4 mm preload or as little as 1 or 2.I'm 220 and I run .44's up front and a 9.8 on the back of my 520 mxc. I had to revalve both ends though. With the fork, you end up stiffening high and low speed damping to smooth it out.