KTM Late Model Linkage Shock Rebuild and Revalve

[Johnf3]

This is not a how to, just a few pictures for those who may be interested. My Husky shock was leaking, so I took the opportunity to tear it down, install a bladder, and do a complete revalve of the compression and rebound circuits. My work bench is lit up like an operating table and it messed up my pictures some.

Shock had to come completely apart. The shock shaft had a small nick in the chrome which I cleaned up with scotchbrite and a light dressing of emory cloth. This picture shows the new rebound stack laid out in order. You can also where I worked on the shaft to smooth out the damage.

Here is the new compression shim stack:

KTMs handle the nitrogen differently than japanese shocks. Instead of a bladder that hold nitrogen they use a plastic disc with an o ring that separates the nitrogen from the oil. Here is a picture showing the differences. The bladder and cannister on the left is what I am going back with. With a bladder system you can service the nitrogen via a standard schrader valve just like every other bladder shock. Stock KTM reservoirs have to be filled with a special connection, converted to a needle fill set up, or drilled for a schrader valve.

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The new reservoir goes on in place of the old and it is ready to reassemble. Here is the shock shaft with the new seal head, new bumper, and new valving. At the bottom of the picture is the rebound stack, then the valve itself, then the compression stack. Further up is the seal head assembly. Everything in it is brand new--bushing, seal, dust seal, etc. The spring under the seal head you see is a top out spring. When the suspension rebounds the spring controls the last bit of travel so it doesn't slam to a stop.

I did not take any pictures of filling the shock with oil and bleeding it. It is a bit of a process. Here is the shock reassembled and ready for its nitrogen charge.

Nitrogen going in. I charged this one to 150 psi.

Here it is all ready to go and install back on the bike.

On the next service in 50 hours or so, I will reinspect the shock shaft where I dressed up the chrome shaft and also keep an eye on the inside of the shock body. These new KTM shocks are known to wear the coating off of the inside of the shock body. Mine looked OK for now but there is one small spot I will keep my eye on during the next service.

 

[Flipit]

I had my shock rebuilt and modified last winter. It made a HUGE difference in the handling/comfort level of my 501.
I hope your results are similar.

 

[Vinny]

You are braber Tham me

 

[bwdmax]

Did you just guess on your new shim stacks based off of the existing and experience or did you follow someone else’s recommendations?

 

[RollingJ]

Nice work! It was much more dramatic when I did mine last winter.

 

[Johnf3]

Did you just guess on your new shim stacks based off of the existing and experience or did you follow someone else’s recommendations?

No guess on this one. The valve is different too so they sent me valving specs around my weight, height, terrain, speed ,etc. The company I used is N2Dirt. Not sure whose valve they used but it is not Race Tech. Also added a low friction piston band as well.

I have been doing my own suspension for a while plus my two boys bikes, certain riding buddies, etc. On my big Adventure bike I came up with the valving myself and it works great. On the front of this Husky, I have a hybrid Ohlins set up that is opposite of what most do when trying to deal with the air forks. Most switch the air side for a spring set up and keep the damper leg. I installed Ohlins internals on the damper side with a spring and kept the air side but run it about 1/2 the pressure (68 pounds or so). Works great.

 

[Johnf3]

On the subject of shims and stack building, my new rebound stack and the compression stack are two stage stacks with cross over shims. A cross over shim is a smaller diameter shim placed after the first set of face shims. On the rebound side you can see the cross over shim after the fourth face shim. The compression side has eight face shims then a set of two cross over shims. When the face shims have a cross over shim underneath them, then they are referred to as the low speed stack.

A cross over shim allows the face shims to open with less oil flow because they bend over the cross over shim easier. You can further tune the cross over by the thickness of the cross over and the diameter. A smaller diameter cross over makes the first stage softer. Thicker cross overs delay the beginning of when the second stage, also called the high speed stack kicks in.

In general, two speed stacks have a softer feel overall vs. single stage stacks. In general!