DIY tuning the Sachs shock

[Kyle Tarry]

I went all the way down to 0.3mm of float and my forks aren't harsh at all.

Did you drop some stiffness out of the mid at the same time you reduced the float? The stock mid doesn't look quite as crazy as the stock base, but it's maybe on the stiff side? Or did you just drop some float?

I am definitely wishing I had pulled my mid. Oh well, baby steps, I will pull it next time.

I think this has pretty much turned into a general re-valve thread, and that's a good thing. It's not like it's so active things are getting buried Anything you want to add would be great.

Definitely a ton of great info, kudos to you for getting this started. I think revalving is something a lot of guys could do if the info was out there, it's not much worse than tweaking a carb or EFI settings, as far as making small/incremental improvements. Like most things, a true expert can wring out that last 10-20%, and they are far more efficient doing it, but that doesn't mean we can't mess around with our own junk, make some improvements, and learn something doing it.

 

[Sparked]

I added 0.7mm of 10mm diameter shims to reduce the float, but otherwise left the stack alone. The full opening of the stack is still about the same since it hits the 17/22mm backing shim at the same point. Obviously, 0.3mm + 0.7mm =/= 1.74mm, so something is wrong with at least one of my float numbers.


I don't expect that amateurs will ever be as good as the factory designers. But, we don't have to be to get better results. They have to get it right for most riders, most springs, and most terrain. We only have to get it right for ourselves, with the right springs, on (if we're lucky) a variety of terrain. So it's a much easier job.

 

[Kyle Tarry]

On the fork side of things, I thought my stock KYBs were pretty good, but I found that I was running the compression adjusters about 15 clicks out on sandy/loamy tracks (for braking bumps and roots), and all the way out (20 clicks) in rocks, and in rocks I was still banging off of stuff.

To try to get a feel for things, I ran a couple of shim restackor comparisons between some stock KTM shim stacks (300 EXC and 500 EXC). The former because it's a similar size/type of bike, and the latter because I've ridden one and it feels pretty good. I found that both were softer than the WR; I don't trust my exact numbers, but the point is general trends.

To start, I've tried pulling 2 of the 6 24x0.15 face shims on my WR. I'd guess this is roughly 10 clicks of adjustment, so hopefully it will put me back in the meat of the clicker adjustment range and give me room to take some more damping out in the rocks.

We'll see how this works and I may play with the midvalve, but for now I did not want to take it apart. 2 shims may turn out to be too much, but I figured it would be better to make a bigger change and see how it feels.

 

[Picklito]

I rode the 144 yesterday and the shock is much improved. Good enough that I'll probably leave it till the next oil change. At that point I may add a little high speed rebound damping, possibly some 36's at the beginning of that portion of the stack as Sparked did.

There seems to be some interest here on KYB forks (glad to see). Here's what I'm running:

Compression
24.11
24.11
24.11
24.11
12.11
22.11
20.11
18.11
16.11
14.11
10.2
11.25
18x1.0*
18x1.0*
10.2*
11.25*
24.11*
* are just spacers and the refill checkplate - they do not participate in compression damping


Rebound
23.11
23.11
23.11
23.11
23.11
23.11
14.11 (will probably move this up one or two positions next time)
22.11
20.11
18.11
16.11
14.11
12.11
9.2
9.2

Mid-valve
24.11
22.11
20.11
18.11
16.11
14.11
12.11
10.3
10.3
22.4

Float
0.8mm

Somebody please try this and tell us how it works or doesn't!!

 

[Kyle Tarry]

Interesting, our shim stacks look slightly different. I have mine written down as having an 11.25 clamp shim, and a 13 where you have a 14. Is that stuff on your bike stock, or did you change it?

I was able to run my bike for the first (real) ride since I messed with my shim stack. I did a good 50 miles of mixed terrain yesterday; rocky singletrack, rocky doubletrack, some hillclimbs, real technical rock stuff, and some smaller sand whoops. I was running 10 clicks out on compression, and the bike felt pretty good. Definitely more plush in the rocks than stock. I was worried about bottoming, but after a couple runs through the whoops I had several inches of travel left. The rest of the day I just rode, plenty of little wheelies over rocks, jumping off embedded rocks, hammering up loose rocky climbs, etc, and never had an issue.

I am hoping to get to the MX track this week, we'll see how bad it is there. I ride 95% enduro/trails, so I'm willing to compromise, as long as it doesn't bottom on every little jump at the track.

My current base valve stack is (everything else is stock):

24 0.11
24 0.11
24 0.11
24 0.11
12 0.11
22 0.15
20 0.15
18 0.15
16 0.15
13 0.15
11 0.25
18 0.5
18 1

 

[Picklito]

Interesting, our shim stacks look slightly different. I have mine written down as having an 11.25 clamp shim, and a 13 where you have a 14. Is that stuff on your bike stock, or did you change it?

I changed it. Smaller clamp to soften overall, and I left the 11 behind it to space things away from the rigid 18's... they'd make for a very RIGID backing plate if the shims made contact.

 

[Kyle Tarry]

Interesting! Good info. Looks like you also pulled 2 face shims like I did; I wonder how much the feel differs between our forks, with that clamp shim being the main difference. I have definitely seen that just a clamp shim change can have a bigger impact than you might expect, although 11 to 10mm is not huge...

How does your midvalve compare to stock?

 

[Picklito]

How does your midvalve compare to stock?

Don't know! I bought the bike with 2.4 hours on it, and the forks already had a tuner's sticker on them, and the seller claimed that it had been "revalved." I didn't like it. I can say that it had only four 24mm face shims on the base valve the first time I looked, and the midvalve was essentially what I posted above. Then, I added the 10.3's to bring the float down, and changed the clamp to the 10.2.

 

[Kyle Tarry]

Some KYB fork updates:

I ran my revalved forks twice now; once on some rocky gnar, and once on the MX track. In the rocks, the felt really great, but I only had to dial the compression adjusters 10 clicks out (I think they were actually 8 clicks out). I went to the MX track today, and the bike was probably too soft. On all the doubles, I have to check up and roll them because any face landings result in pretty harsh bottoming. I had the clickers 1 click out, still no good. Now, I am not sure how much of a compromise I can get between these polar opposite types of riding, but I'm going to try! The way I see it I have a few options:

1. Put one of the face shims back in.

2. Add oil (currently at about 100mm)

3. Tweak the midvalve (less float?)

Some uneducated guesses about these options:

1. I am going to do this, but I don't think it'll help that much. It will probably help get my adjusters back into a more useful range.

2. Won't hurt, and I will probably add a bit, but I don't think it will be enough.

3. I think this is where the solution lies. I'd like to try taking some of the float out, since it seems like there is a LOT of float stock. The biggest risk here it that it'll make it harsher on the trails, but it seems like I ought to be able to bring the float down to 0.8mm, which is still pretty damn big, and have better bottoming resistance than stock.

Comments? Tips?

 

[Picklito]

The only spec you've got that isn't already "on the map" is that large float. I'd take it right to 0.8 with no other changes and see whatever good or bad qualities that adds to the fork. I don't think you'll be too harsh.

 

[Kyle Tarry]

I think you're right. From everything I've read, 0.8mm is still pretty big. The only problem is, I have to take the damn cartridge apart.

If I put the cartridge in a good tube clamp (so I don't crush it in a vice) and make a tool to unscrew the top, I should be able to get it, right? I think there are some peens I need to drill, is there also loctite? I have full shop access and can weld/machine anything, so it can't be that hard...

FYI: I haven't taken mine apart yet, but my notes say that the stock MV is supposed to have 4X 24.11 face shims and then a tapered stack (20, 18, 16, 14, 12, 10). Might be tempted to pull one of the face shims at the same time I reduce the float... Gonna check it out in ReStackor.

 

[Picklito]

I currently have bikes running WP, Marzocchi, and KYB forks, and darn it... I can't remember off the top of my head what that KYB looks like inside. But, all these open-chamber varieties are essentially identical inside, and none of them are difficult to disassemble (or I'd remember!!!). The only "special" fork took I have is the set of soft jaws on my vice, which have a nice V cut into one side. I never clamp the cartridge tube, but using these jaws you can clamp on the more sturdy piston rod without scratching it. However, the cartridges usually have just enough vent holes and hex shapes on them that you can get a wrench here and a rod through there and unscrew them.

As for peening, sometimes they are peened at the nut that holds on the rebound/midvalve piston. Just grind off the last few threads then work the nut back and forth, lubricated, to get it off without stripping the tiny male threads. Shockingly, and more commonly, I find that the nut is already loose! Take the usual precautions: One cartridge at a time so you have the other to use as a reference when you accidentally knock it off the workbench and the parts play hide-and-seek across your shop floor (or so I've heard).

 

[Kyle Tarry]

Hm. For some reason I thought I read that the cartridge itself was peened somehow. The peening on the midvalve nut doesn't worry me one bit!

I have a couple business trips for the next few weeks, but as soon as I get back and have a free moment, I am going to take one of these guys apart. I'm going to leave the BV how it is for now and just change the MV. My next several events are rock runs anyway, so I don't need the bottoming resistance and the current plushness is good!

 

[MOTORHEAD]

I probable told you that. Some of them are. Not sure when they stopped doing that.

 

[Kyle Tarry]

No worries. I'll take mine apart and get her opened up in a couple of weeks, I'll snap a couple photos. I'm not too worried about it!

 

[MOTORHEAD]

It's pretty easy to tell if they are. You'll see the dimples in the top of the cartridge tube where the seal head screws it.

 

[Picklito]

I'm going to leave the BV how it is for now and just change the MV

This will be helpful for all of us, to see just one change at a time. Thanks!

 

[Kyle Tarry]

Alright guys, really stupid question, don't make fun of me too much.

I have a couple of bikes I am trying to replace a midvalve check plate with an actual shim stack, and I'm not fully understanding what the whole assembly should look like. I've sourced a cup washer, 2mm and 5mm long 6mm ID x 8m OD sleeves, springs, and shims, but I feel like I'm missing something. I don't understand what the shim stack "bottoms" against after it takes up the float and compresses the spring.

This picture (http://i2.photobucket.com/albums/y15/tacubaya/midvalve.jpg) makes some sense, basically showing a larger diameter sleeve under the spring, that the backer shim will bottom on, and then the normal smaller (8mm OD) sleeve that the shim stack slides on. However, the springs I got from Jeremy at MX Tech are just over 8mm ID, so I can't run any sort of a larger diameter sleeve under them.

Can anyone help me out, or draw a little picture or something?

 

[Sparked]

I think the plan is that the top shim in the stack (the support or backing shim) hits the cup washer. That's similar to the KYB forks on Huskies. Like this:

The rightmost of the three pictures is missing the cup washer.



Other forks (like WP) have the backing shim hit a shoulder, the spring is a larger diameter and fits over the shoulder. It's just like the picture you linked except that there are no little shims on the inside of the spring. The point of the setup is that the shim stack hits something before compressing the spring completely. You might re-use the check plate shim as a backing shim.

 

[Kyle Tarry]

Brilliant thanks Sparked. I was wondering if it was supposed to bottom on the cup washer.

On my DRZ, there is a larger diameter washer-and-sleeve assembly that I could turn down on one end to put the shims on and have them hit the shoulder, but I would need to use a larger ID spring than the one Jeremy sent me.

Thanks dude!