4CS fork revalve question

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cerealkiller
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Re: 4CS fork revalve question

Postby cerealkiller » Tue Aug 22, 2017 1:14 pm

axel99 wrote: I will dig up some details tomorrow.


Still waiting Alex. :D

I'm guessing this is the "Terry Hay" mod I read about on KTM talk? Did you do it to your forks?

I found it difficult to follow given that information on it is spread out on 50+ page thread and I have only a seal-and-bushing-swap level of suspension knowledge. If you actually did the mod though I'd be interest in picking your brain. :thumbsup:

Edit: forgot to add, my understanding is that you would have to work out your own valving stacks after doing the mod. Another reason I didn't get further into it. I think the inventor was originally helping people out with a baseline, but I don't think he's an active poster anymore.
-Jared
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dirtyboy
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Re: 4CS fork revalve question

Postby dirtyboy » Wed Aug 23, 2017 10:05 am

Hey,

I did not feel a re-valve was necessary on my 2016 350XCF. However, I did make changes to compensate for the forks. Here is what I did:

  1. Set springs to match my weight. This needs to be done on all motorcycles as the first step. In this case, it was 4.2 N/mm front and 45 N/mm rear.
  2. Set fork preload washers to 3mm. (468mm total spring/washer length ends up being close to 0 mm preload) Bike came with 6mm of washers so the preload ended up being 3mm and the total length 475mm.
  3. Race sag set to 100mm instead of 105mm. This puts more pressure on the forks and makes them "feel" softer. Static sag was a little lower than suggested at 44mm
  4. Oil level on fork was set to stock 65mm (this should be set according to bottoming) 85mm oil height makes you use more travel. I messed with this and it is very adjustable.
  5. Stock clicker settings, except for the shock high-speed adjuster set to 2.5 turns out (Makes the rear more compliant on fast things like roots and rocks)

If you are faster or slower than me than I would work on the oil level first. Then adjust the race sag according to the front wheel traction. (Lower for knifing [turns too sharp] and raise for skidding [doesn't turn well]). I notice that the knifing and skidding can also be controlled by body position and I used to have problems late in races with my body moving back on the bike when I was tired and the result was the bike didn't turn and I'd go down on a simple turn.

Just an alternative to having someone re-valve and tell you what the settings should be based on the re-valve.

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cerealkiller
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Re: 4CS fork revalve question

Postby cerealkiller » Wed Aug 23, 2017 10:46 am

Because my 2012 350xcf CC forks were so good, I was considering it long and hard but I also did not re-valve my forks on my '16 350xcf.

Like Dirtyboy I swapped the springs (though in my case to much stiffer ones), removed the spacers (maybe a little overboard on my springs), removed 15mm of oil, run 2.5w oil (Alex's recommendation) and I have precisely 103mm of sag (Dobi's recommendation).

The 4CS still pales in comparison to my old re-valved CC forks, but it's livable. I still experience some mid-stroke harshness, they bottom a little easier than I would like and are a little too bouncy even with the rebound dialed to the max. That said, they move over the little stuff now and don't clank as often.

YMMV though. My recipe is no doubt related to the stiff springs I'm running. E.g. the bounciness is probably due to the stock valving not adequately controlling my stiff springs, then made worse by the lighter oil.
-Jared
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axel99
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Re: 4CS fork revalve question

Postby axel99 » Wed Aug 23, 2017 11:05 am

Here are the links to all the details, its a long read but alot of the usual peanut gallery noise. The guy that seems to know some stuff about 4CS (Terry Hay is a auzzie tuner) so really pay attention to his posts.

https://thumpertalk.com/forums/topic/1140457-ktm-4cs/?page=2
http://ktmtalk.com/showthread.php?508914-4cs-fork-answers

Basically I did this
- remove check valves
- drill 1mm hole in midvalve
- instal Race Tech gold base valve and comp adjusters (Kit 280601G and FACB M3010001) as per install instructions
- reassembled with same preload and oil hieght as before mods

So the rebound will then be at the top and compression will be on the bottom. Do NOT convert to OC configuration!

You can do the fix cheaper but you will need to do alot more reading and sourcing individual shims seemed stupid expensive.

Building the bottom comp stack took some effort, the shims in the kit are not marked so you need to measure them with a micrometer or a really good caliper may also work. Took some time at the kitchen table to sort out :) I am just using a recommened setup from the RaceTech but the base valves have alot of valve shiming options for the tinkers out there. I was so happy with the first attempt I never touched it again. I am sure it can be improved but after suffering a 100hrs on stock valving these mods seemed like magic.

When removing\installing the mid valve the threads on top of the inner rod must be covered or you will tear the small oil seal. I just used some teflon tape to cover the threads, other than that it was straight forward.
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Re: 4CS fork revalve question

Postby markvfr » Thu Aug 24, 2017 7:15 am

axel99 wrote:When removing\installing the mid valve the threads on top of the inner rod must be covered or you will tear the small oil seal. I just used some teflon tape to cover the threads, other than that it was straight forward.


You can also unscrew the spring guide, flip it and thread it back onto the rod and access your midvalve while still in the cartridge eliminating the risk of damaging the purple seal.

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