DEFECTIVE 4CS FORK!!!

[Duncan]

Here's a good one:

I just dismantled my EX 4CS fork and when I removed the 17mm allen on the bottom the base valve fell out dismantled, with the aluminum post completely unscrewed from the 10mm hex nut and the shims totally loose and 'floating' non the post!

This was the rebound side and explains why I noticed poor fork performance during my last ride and topping out with a clunk.

The compression leg was found with an intact base valve but it was only finger tight!

See post : EX Suspension.

Could this be a KTM (owns WP) plot against Alta to booby trap the competition?

In any event I recommend all 4CS owners to check tightness of the 10mm hex nut that sandwiches the base valve shims.

This photo shows how the dismantled base valve plopped out onto my bench:

 

[Philip]

KTM and Husky had a recall on 4SC forks back in late 2015. Things were loose inside those forks.

My 2015 Husky was not torqued tight either. The damping was crap, so I took it to a local tuner after riding it for 15 minutes and maxing out the clickers. A month later I got a recall notice in the mail.

It is not likely that this female bottoming cone actually separated from the base valve while the fork was assembled because then the male cone at the end of the damping rod would have mashed it into a pulp, damaging everything inside the fork. It was probably very loose, and then came completely undone when you were unscrewing the base valve. You got lucky! I heard stories of people needing complete fork replacements due to this.

When I told the dealer that things came apart when we removed the base valves, he immediately asked if we used an impact gun. We weren't.

The torque specs on this M6 screw is not very tight, I forgot either 3.5 or 7 Nm (31 or 62 in-lbs), either spec can be used. But you have to use a few drops of red Loctite on these threads. Same on the mid-valve and the male bottoming cone.

 

[Duncan]

Good info.

I was wondering about the mash factor also,

possibly the cone stuck to the tapered rod and rode with it and if i didn't bottom out during that period - no mashing?

Your 2015 Husky was loose straight out of the box and you rode 15 minutes, felt crappy, took to tuner and he found loose stack?

 

[Philip]

possibly the cone stuck to the tapered rod and rode with it and if i didn't bottom out during that period - no mashing?

No, not possible. There is quite a clearance between the two. Also, the base valve shims would have been all over the place.

Also, your rebound was unaffected. The base valve only controls compression.

The only difference between the two legs of the 4CS fork is that one of the check valves is upside down. The Alta specs calls to install the compression leg's check valve the same way as the rebound leg's check valve. Double rebound adjusters at the top. Then to adjust your compression you will need a pair of Race Tech base valve, which have compression adjusters in them.

Your 2015 Husky was loose straight out of the box and you rode 15 minutes, felt crappy, took to tuner and he found loose stack?

Yep. Exactly.

 

[p0wn]

I'm having this issue as well. I hear a loud clunk when I compress the forks fast. I thought it was my steering stem that was loose or something. It's pretty jarring. Is the only solution to take this to a suspension person?

 

[Philip]

I'm having this issue as well. I hear a loud clunk when I compress the forks fast. I thought it was my steering stem that was loose or something. It's pretty jarring. Is the only solution to take this to a suspension person?

If you want to try riding a little faster, I would take your bike to a suspension tuner and ask them to install these shims into the fork and shock:

Factory developed Redshift MX suspension shim stack specs