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Harsch Front fork KTM -04

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My front fork feels really harsch and on tracks with alot of stone, the hits goes right up in to the arms.

The WP forks seems alot diffrent from the Japanese forks. The Japanese is alot smoother and nicer in really rough conditions.

The fork is standard all through but serviced with new oil about 10 hours ago.

I have to run with the compression screw all out to make feel OK.

Any ideas?

Peter

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what do you weigh? what bike?

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your fork springs are way soft so that will mean its riding in the lower part of the stroke and you will be sitting on the airspring and this will feel harsh, with the stiffer springs you should be able to use a lower oil amount(airgap) start at the minumum, that would also help, however you also have the clickers at the softest setting so i would think the valving is too stiff.

this is what Race tech recommend for your weight

Recommended Fork Spring Rate: 0.456 kg/mm (use closest available)

Stock Fork Spring Rate: 0.42 kg/mm (stock)

i did one of these forks for a freind , he weighs the same as you and he uses it just for trail riding, i ended up removing 3 of the 6 face shims on the base valve as he also had the clickers fully out, he likes it now, i am sure a wp expert could alter the mid and the base to make it a much better fork but removing a few shims did the job he wanted with no real need for testing.

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Could you help me pin point the shims that i need to remove? Is this procedure hard?

Thanks for the help. I will try to get some new springs.

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if you remove the base valve, then remove the nut on the top of the base valve, you then remove the spring, then the piston, you will see a bunch of shims-you need to remove 3 of the 24mm wide ones, then refit the assembly in reverse of removal, use a little non permanant threadlock on the nut and also when you refit the base valve.

Is it hard?-not really if you are mechanically minded and take your time, you will need a airgun to remove the base valve.

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I`ve found some new springs on Ebay and they are rated as such "3,8 / 4,0 / 4,2 / 4,4 / 4,6 / 4,8"

I guess i should pick the 4.6?

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a 4.6n/m is actually 0.47kg/mm so no thats too stiff, go for the 4.4n/m which is a 0.45kg/mm ,yours are a 4.1n/m now.

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i ended up removing 3 of the 6 face shims on the base valve

the standard setting for the base is:

6 - 24 x .10

2 - 22 x .10

1 - 20 x .10

1 - 18 x .10

1 - 16 x .10

1 - 14 x .10

1 - 9.5 x .30

1 - 18 x .25

maybe you want to pull one 22 as well

Many other variations still possible if still too stiff.

The Mid has 5 x 24.10 and one 22.10

i'm not really a fan of such a stack and would rather like to see a tapered stack.

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I found a set of RaceTech springs,just the ones i needed, a couple of miles away and i put the in today.

Just a little question since i forgot this while i was trying to put it all together.

The nut hat holds the Shim assembely,should it be drawn tight och should it be drawn flush with the bolt so the valve could move?

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I found a set of RaceTech springs,just the ones i needed, a couple of miles away and i put the in today.

Just a little question since i forgot this while i was trying to put it all together.

The nut hat holds the Shim assembely,should it be drawn tight och should it be drawn flush with the bolt so the valve could move?

Nut gets tightened so piston can NOT be turned on stem. Then the thick shim just under the nut MUST be able to be moved against the spring.

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Great,thats how i put it togehter.

I followed the tips regarding the shims and removed three 24mm shims and filled it up to 120mm airgap.

People i`ve talked with overhere says that you could use a 150mm airgap and that way smoothen out the fork?

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Great,thats how i put it togehter.

I followed the tips regarding the shims and removed three 24mm shims and filled it up to 120mm airgap.

People i`ve talked with overhere says that you could use a 150mm airgap and that way smoothen out the fork?

hey there!

WP recommendation for your suspension for 75-85kg riding weight is as follows:

Rear spring: 80 N/mm ... description (62) 80-250

Front springs: 4.2 N/mm...(mog already got you on the right track here!) length of spring with spacer 523mm, 5wt oil and 110mm air chamber.the air chamber range is from 80 to 130mm max...

Please note that this recommendation is made to suit the majority of riders, etc...(but should be no need to go beyond the 130mm max air gap) so is the shim stack... meaning if you are above average rider you could benefit from some sort of revalve... hope what you tried worked out for you! its all trial and error anyhow for each rider... try to enjoy the learning from it if nothing else!

you should also check that the shim stack is the same in both forks! before 2005 or maybe a bit earlier it was common to have incorrect shim stacks and missing shims or wrong shims in the stacks in the fork legs...affecting performance

if you have not yet serviced your forks its possible that they are not working properly - last one I did was from 2005 450 EXC and the needle was stuck - meaning there was no rebound adjustment... never had been properly serviced... some shims were also bent, and the new oil inside the fork was already contaminated after 2 hours of riding because the customer didn't clean everything (every shim, etc) and the oil seal was full of dirt because he wrecked it trying to put it into place with a screwdriver (not even a homemade PVC seal driver!)🙂

cost him double in the end!

good luck!

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