Service KTM (WP) Shock and Forks - Tips and links

KTM (WP) – Shock and Fork Service

In this case for a KTM sx-f 250 2006. Most of this thread should apply to the 250-450’s for years 2005-2009 (don’t quote me on that)

Just thought I would send out a post to perhaps help others who are inclined to service their own suspension.

Personally I have never owned a KTM steed. This recent effort was to help out a buddy who picked up a 2006 sx-f. When he got it home the first thing I noticed was general care and maintenance on this bike was for not. In my experience when an add says “never raced” – usually means something far worse = Never properly serviced or maintained. A fate much worse than being flogged at the local race track. Second was the back shock was shot and leaking oil. Being that I love wrenching I said I would sort out the back shock. 25hrs or so later, and a complete tear down. The bike looks new again.

Here are my learning’s, tip and relevant links that took hours to find.

Shock:

Basic step by step

A good step by step form “ADVrider”: by Tseta

http://www.advrider.com/forums/showthread.php?t=653302

notes: shock was similar, other than the rebound section.

Service manual links: (this is the manual that supported the shock I was servicing)

http://slorider.com/ktm/manuals/wp5018pds2003.pdf

Schrader valve mod:

Again WP coming up with an elaborate tool to ensure you have no choice but to get it serviced by your local KTM dealer at a less than kind price. Suffice it to say modifying the “piggyback” cap took less than 10 min and cost 2 dollars.

Step 1: Buy a NPT (Schrader valve)

Step 2: Drill out cap (11/32 drill bit which is standard for NPT valves)

Step 3: Tap using a standard NPT tap

As you can see it comes out pretty clean and easy.

KTM.jpg

As an alternative you can also use this from racetech:

http://www.rockymountainatvmc.com/p/44/54/280/1066/4149/5854/Race-Tech-KTM-Bladder-Cap-Kit

Shock Oil:

Again KTM or WP being bastards by charging double per liter for their shock oil. Thus, I obviously look at alternatives.

I have been using Peter Verdone Designs web site for years for my MTN bike suspension. I cannot thank this guy enough for his chart on comparing various oils.

http://www.peterverdone.com/wiki/index.php?title=Suspension_Fluid

In this case, WP uses fairly thin oil than others. I used Maxima 3wt for both the shock and the Forks.

Purging air bubbles:

Another stoooped tool KTM insists on that is not necessarily required and can easily be replaced by gravity and patience. Best part on this video is at the 13min mark.

Rebound Adjuster:

While I’m bitching about things; WP came up with the worst piece of engineering that I have seen in a long time. See pic – now I will give you 1 guess where that sucker is going to snap if it goes to the stop or gets corroded into place – which btw is often. So much so you can get a mod to prevent such a thing.

In my case I just added some Teflon tape to the retaining nut that secures the adjuster in place.

KTM-3.jpg

Charging the Piggy Back;

Not to start a war here but air vs Nitrogen. I completely understand the merits of charging with nitrogen. It’s an inert gas that does not contain moisture and is not as subject to change by heat as air can be. Personally if you can get it charged for a few bucks at your local auto stop – sure go ahead. If you could not be bothered air is fine in my books. Never been an issue on my mtn bike units.

Other than that slap it all back together and it’s good to go.

Forks:

For the most part same as other brands to work on.

The only thing I struggled to find was the oil level – which is set at 100mm (thanks to frezno) from the top of the fork tube compressed all the way down on the stanchion, compression rod in place and spring out.

Very nice write up!

jw

This is a great thread.. I have been wanting to get the rear shock of my '07 EXC revalved for a few weeks now, right after I finished revalving the fork actually.. BUT.... in the spirit of DIY...

How hard would it be to revalve a WP shock at home? Before you answer I will say that I am a very experienced "shade tree" mechanic...I have rebuilt many car and motorcycle engines, have and operate a lathe at home, have done several fork shim shuffling jobs, tune carburetors, tune ignitions, and have basic machine shop measuring tools and instruments.

I've seen it done, watched a few videos, etc. I'm not sure I'm completely prepared to tear into it yet.

Race tech will have you believe that you need to buy every tool they sell for the WP shocks. That's about $2500. Might as well send it out..

Anyway, how many of you have been discouraged about revalving a shock at home? Have you done it? What was holding you back?

I can find recommended stacks, and once I am comfortable with taking the shock apart and successfully reassembling it, I would probably do it often until I found the right feel.

I'm not scared of it, I just don't want to break anything or not be able to put it back together.

Shops charge $250-400 for the revalve on the shock alone I noticed. Can I do everything at home except for the nitrogen fill? I noticed the Race tech bladder kit that allows you to charge with a Schrader valve so you can do everything in the garage.

Edited by Bailey28

@Bailey - to redo the shim stack on the shock would be a snap. As long as you say you have the shim configurations you think you need its pretty straight forward.

Basically once you separate the compression bolt (which has all the valves and shims etc) it is basically all apart from there. For me all I needed to do was replace the main oil seal. As soon as you remove the top bolt everything slides off the rod. I basically slid everything onto a screwdriver so that I would not get any of the shims, valves washer etc mixed up.

For you - you would basically remove the top nut then each subsequent part an lay them all out in sequence on your bench. From there, you redo you shim stack and reassemble.

When your done PM me I would like to know what you did differently and what was the result.

As for special tools - I did not use any. On the piggy back I used 2 drill bits and a long "Jimmy bar". I did the same for the forks too. Also a crap load of heat for good measure (heat gun). Yes its nice to have the rights tools, but I grew up in the bush of Africa and I take a deranged pride in making do with what you have. Just take a little extra care is all.

Cheers

By the "piggyback" are you referring to the bladder cylinder under the compression screw?

My shock does not have an external high speed adjuster on the EXC. I have only low speed and rebound at the bottom.

With revalving is there an need to remove the compression adjuster screw?

Thanks for the encouragement as well.

By the "piggyback" are you referring to the bladder cylinder under the compression screw? -Yes

My shock does not have an external high speed adjuster on the EXC. I have only low speed and rebound at the bottom.

With revalving is there an need to remove the compression adjuster screw? - yes, as that is where you will purge the last bit of air and top off the oil. Not to worry, it's pretty easy to remove, as it comes out as one whole unit.

Thanks for the encouragement as well. - NP.

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