How do I adjust WP 43 forks?

[slowdude]

Hello, I am new to KTM, and just bought a used 2000 400exc. I like the bike a lot and Im trying to get the suspension dialed in for me. I see the rebound clicker on top of the roks, but dont see any way to adjust spring preload or compression damping.
Would the stock springs be appropriate for me? I weigh about 155 (unclothed) and ride mainly high speed, bumpy fire roads. I am looking for a plush ride.
Also, the top of the fork legs, at the rebound clicker, is anout a quarter inch above the top of the lip at the upper triple clamp. Is this stock?
Thanks for any help, Colin

 

[Jeff Gilbert]

Retracted advice from posting without sleep .

I would think if the forks are stock your weight would be okay to a little soft.

 

[dawiev]

Hi, I run a 2000, 400SX and I'm a bit more than 155, but close. Jeff is right that the stock springs would be about right for you. But, you've got Upside Down forks and not conventional and thus not the rebound/ comp combination.

The previous owner raised the forks in the triple clamps to make it turn a bit faster, but this might make it more unstable at high speeds, you can try and lower it progressively back to level with the top triple clamp (level is the factory setting). The G-spot will be where it feels as stable as possible at high speeds, but not push the front out wide in turns. The quality and make of front tyre will also play a big role in this.

Make sure that the rebound clicks (at the top) are the same for boths forks. The compression is at the bottom fo the fork - on your back with a flat screwdriver. Make sure they're the same on both sides.
I found that the rebound was way too fast at factory settings, but the compression close. Have fun !

 

[dawiev]

A couple more things -

I would suggest you give the forks a good clean and service - take them out and put new (good quality !) fork oil in. It's been probably working hard for over 2 years now, so before you start changing the settings, give yourself a solid base to work from.

Also let the air out of the forks frequently after hard rides - BUT be careful as they are soft and will strip very easily (star screw at the top of the forks) If you don't do this, the bike will feel very different and the forks hard and uncompromising on the 2nd and subsequent rides.

 

[Jeff Gilbert]

Oops! Sorry for the wrong answer on the adjustments. I should have known better than to reply while I was asleep. :confused: When I saw 43mm I instantly thought about the zooks I used to have where the adjustments were as I described.

 

[slowdude]

Okay, thanks for the helpful replies. I know that the previous owner had the forks revalved to be more plush, but the springs are original.
To bleed the air, can I just unscrew the star screw and let the air escape? Also, compression on bottom of forks is clockwise to increase compression?
I like the way the bike turns right now. It has a steering stabilizer, so stability has been pretty good. I know the PO weighed about 20 lbs more than me, so I wanted to try softeniing things up a bit and see if it was more suited to me.
Colin

 

[Shaw520]

Originally posted by slowdude
I weigh about 155 and ride (unclothed) mainly high speed, bumpy fire roads. I am looking for a plush ride.

First thing you'll want to do is put some cloths on when riding that thing!! ;)

 

[slowdude]

Good catch. I guess the wording was a little ambiguous. Unclothed riding does not take place here other than days with temps over 90 degrees.

 

[slowdude]

Okay, so I found the compression clicker at the bottom of the legs. Is there any wayto check what the previous owner may have done to adjust the spring preload?

 

[dawiev]

Hi, sofar - with the steering damper I wouldn't suggest you lower the forks. They also respond well to revalving so you have a very good setup if dailled in properly.

Preload - unless they have the aftermarket preload adjuster caps installed, you have to manipulate this with springs and oil level (strange, the terms preload and sag is used interchangeably) This is the first thing to set up before you set the rebound and the cmpression (preload and compression is two different things) I would suggest you download the fork manuals from the Ohlins website. They give a very good method of checking the preload/sag and what to look for in setting compression and rebound.

I would not suggest that you try to compensate for the wrong preload setting by making the compression softer. So check and set the sag/preload first. The race sag/preload is more important (you have to do this with your clothes on - sorry !) than static sag. Then work on the rebound and comp.

 

[Shaw520]

SD, Everyone here is correct, you must first set preload, race sag should be between 3.5"-4" (95mm-110mm). That is how much the bike should sag w/you on the bike in race position, with cloths on! Usually 90-95mm in the front and 100-110mm in the rear, seems to work the best. Once you have that set, there is a very inexpensive fork shim kit ($39.95) that can be purchased through Chuck Wagoneer that will soften the compression and make the fork as plush as you want, (4 different stages of dampening). But remember,.....plushness begins at the top of the stroke, if you are riding half way down the stroke, they will never feel plush. Good Luck, PM me if you need further info.

 

[euro gasgas]

The WP fork manual can be found on the gasgas rider's club website (along with gasgas parts manuals for when you decide to buy a gasgas! ;) ).
Check out www.gasgasrider.org. There are also pics of the gasgas '03 models from the U.S. gasgas dealers show - look under news.

For roots and rocks most set the oil level at 150-155mm. I use either spectro #2 shock oil or spectro SX fork and shock oil. Either of these are approximately 5W and have a viscosity index of around 400 (virtually fade free performance).

On the topic of spring preload, it will be determined by shims - you'll have to pull off the fork caps to check (this is probably described in the WP service manual) . You can buy caps that have externally adjustable pre-load - they are made by WP - I think ligne racing is importing them - www.ligneracing.com.


jeff
www.gasgasrider.org GasGas Rider's Club

 

[slowdude]

Thanks for all the good helpful replies!

 

[euro gasgas]

By the way, the WP fork needs to have the mid-valve disabled when they are revalved in order to be plush. Swapping out a few shims will help but will not get you all the way there. Some suspension tuners do this and some don't; The cartridge needs to be cracked open in order to do this modification (and its alot more work).

lt-racing does this along with modifying the internals to improve flow even further (okay, so I am spamming for my best friend! I plead guilty :scream:) His prices include shims and oil so there are no surprises when you get the bill...

jeff
www.gasgasrider.org GasGas Rider's Club
www.lt-racing.com GasGas Performance Products and Services

 

[jeb]

I haven't heard of any KTM guys disabling the mid-valve so that may be more of a GG thing. The forks are similar but not exactly the same.

 

[euro gasgas]

It's not just a gasgas thing - for off-road, the mid-valve is generally a bad thing and causes harshness over abrupt hits. Whether it be a gasgas WP fork or a KTM WP fork, they both have a mid-valve and have the same internals. If it was my choice, I would disable it...

jeff
www.gasgasrider.org GasGas Rider's Club

 

[Gardener]

How do you disable the mid-valve? I've installed Chuck's kit and changed oil/seals but that's as far as I've ever been into a fork. Sorry if the question is simplistic.

 

[marcusgunby]

A midvalve can be made to operate like a check plate-just make it have alot of lift and very stiff.Thats the beauty of the midvalve it can be anything you want.

 

[KTM-Lew]

The stock KTM set-up is a check-plate, (3)24x.1shims and a spring for 01.....I'm not sure how much more you could disable it. :confused:

The 03 has a shim stack/mid-valve. A mid-valve in and of itself isn't a bad thing....proper application/configuation is superior to a check-plate system.

Gasgas....I'm not sure where you got the impression it was alot of work to get to the mid-valve or if your tuner told you that .... after you remove the spring guide and the base-valve the cartridge rod will drop out....the mid-valve is on the back of the rebound piston. :cool:

 

[euro gasgas]

Thanks KTM-Lew -
In terms of dissassembly - I was thinking of the older 40mm WPs. I used to work on my own suspension - now I just send it to Les @ www.lt-racing.com. He also does a couple of "machine operations" to modify the fork and improve flow (I am no machinist and he is). I did call Les earlier todayand he did tell me the cartridge slides right apart as you say.

The spring that is used for the checkplate on the rebound piston is quite stiff so that it acts to restrict flow - to get it to act as a simple checkplate a lighter spring is needed.

Everyone has different tastes and different terrain to deal with - my experience has been that mid-valves hinder the forks ability to give plush action in tight technical rooty, rocky stuff (that is typical here in the northwest and in the northeast). YMMV.

jeff