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Forks Still Harsh

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Running KLX 300 forks on my KDX. They were a huge improvement over the stock ones. I want to make it clear here that I am not looking for mx forks on this bike. I have a spare set of KX 125 forks that I MAY swap on if I have no other options, but for what I ride they would require a full re-spring and re-valve, and I'd need to do some custom axle work. For how much I ride the KDX (I ride my KX125 WAY more on the track) It doesn't make sense for me to go all out on the off-road bike.

 

Now, I did the fork swap, and they were very plush. I'm a B/C rider, 180lbs. Resprung the KLX forks this year with .48kg/mm springs from RaceTech which were what was recommended for my weight. I seemed to have solved one problem, and created another. I re-did the seals, new oil (5wt) and set to the factory level. I've rebuilt lots of forks before. The springs made for a huge improvement in the slow/big stuff, but over the faster small and sharp bumps, the forks are now worse. I've played around with the clickers (compression only on these forks) and can't seem to get them any better. I'm even religious about bleeding them once they heat up.

 

TL;DR:

 

Resprung forks for my weight. Now much better on large "soft" hits, but harsh on sharp / fast / repetitive stuff. Is a revalve required? Modify the shim stack? Any suggestions you guys could provide are greatly appreciated!

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Sounds like too much rebound

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What were the stock springs?  Are the 0.48s stiffer or softer than stock?  I assume they are stiffer, so it would probably have relatively "less" rebound than it did with the stock springs.

 

0.48 seems stiff to me for a 180 pound rider on a woods 2-stroke...  I'm 175 on a 300 2-stroke and I run 0.44s.

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My mistake, they are 0.46's not 0.48's. the stock ones are stupid soft, for a 140lb rider. 0.32's or something.

I'm not opposed to modifying my shim stack for more rebound if need be.

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As simple as it sounds you may try SKF fork seals. They allow the forks to move with less stiction and improve the feel and traction of the fork by reducing friction.

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I would try 2.5 or 3 weight fork oil first at the factory level. I also think the .46s may be a little stiff.

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.46 springs are probably still too much but what kind of valves does this thing use? Is it a traditional valve, reverse bend or something else? Also, what is your oil height?

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I'm not opposed to modifying my shim stack for more rebound if need be.

What mog said. Try less.

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Stock springs in those forks are 0.38.  Seems unlikely (but possible) that he would have too much rebound even after going up 20% on spring rate.

 

Since you don't have rebound clickers, you could try lighter weight fork oil like George suggested as a way to see if less rebound helps.  Probably is it may also mask the problem by lightening compression at the same time.

 

0.46 springs seem stiff for your weight on that bike.  Since the bike was plush before you changed the springs, and is harsh now, it seems pretty likely that it's a result of the significant increase in spring rate.

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Might even swap one .38 back in for one of the .46s. I have had tuners say that is too big a diff in weights but for your use I can't see it hurting anything.

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The springs are correct for my weight. Even still coming off something as small as a 4' to flat drop, I will bottom them out. With the stock springs it was so much worse.

 

I'll maybe look at putting gold valves in?

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Well, the forks worked were plush with the other springs and with no change but the new springs they're harsh, so obviously the springs are a factor.

 

If you're having bottoming issues, you can try raising the oil level, or adding highspeed compression damping to the shim stack.

 

I highly doubt a gold valve kit will solve your problem, a normal shim stack modification would probably be sufficient.  Given that you're having trouble on smaller hits, it's unlikely that the piston orifices are causing damping spikes due to flow restriction.

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