DIY tuning the Sachs shock

ya, fill it with 20-30 psi before putting your oil in...

So, how did this work out?

I think the manual says 1/2 way, but I set it more like 2/3's of the way in.

Sachs manual? How do I get one?

No, it's covered in the Husky shop manual.

It worked out quite well. I rode the Desert 100 in Washington the other weekend, which is mostly rocks and whoops. It handled the rocks really well- the front was much more planted than before. I've got some more changes planned to help with the whoops. I'll go a little stiffer in the rear rebound damping, and completely re-do the front compression damping. I know what I want in terms of the current valving and clicker settings, so hopefully the software will steer me right again for the stacks.

I have some shims on order, so will see what I can do when they get in.

Good deal. Hey, thanks for turning me on to the program. I've spent some time going bacl over some of the stuff I've done in the past using the program and notes I have, so I can get a better idea of what it's telling me. Should be a big time saver, once I invest the time to understand it.

Been following your thread, but only now watched the video... now that is some cool stuff!! Was that video before or after the fork revalve? The rear sure looks planted!

HUH?!?!?!? Obviously I'm not on the same page as you guys (which I've been wrong ONCE before). Are we talking about the nitrogen piston?

Yes, reservoir (nitrogen) piston. Motorhead says the spec is in the manual but I sure can't find it!

OK, I'm wrong. I can't find it either. May have been a different shock manual. Blake is right.

Ok, I made some progress, and then got busy so didn't post any results. I've done basically the same thing to the compression valves (both front and rear) that I did to the rebound valving. And, I increased the rear rebound damping to fix the kicking. It's still not perfect, but it's all been forward progress which makes me really happy.

Starting with the rear rebound. It mostly felt good but kicking more than I liked. I did the spring-mass-damper calculations and my first stack had a damping factor of 0.84. The new stack has a damping factor of 1.02. It works way better. The back tire still sticks, but there's no more kick. For the SMD calculations, I used 6.0 for the spring and 54kg (120#) for the mass. That is my guess for the sprung mass of the back of the bike.

The stack is:
38 0.250
38 0.25
24 0.250
36 0.25
36 0.25
36 0.25
36 0.300
34 0.300
32 0.250
30 0.300
28 0.250
26 0.300
24 4

This is the same as the previous rebound stack with 3 36x.25 shims added to the high speed side. I also switched from 6wt to 5wt oil.

Compression on the rear was just a wild guess, but it seems to have worked out.

Stock:


44 0.20
44 0.20
44 0.20
44 0.20
44 0.20
44 0.20
44 0.20
44 0.20
44 0.20
44 0.20
36 0.20
40 0.20
38 0.25
34 0.25
30 0.25
26 0.25
24 0.25
22 0.30
20 0.30
36 5.00

Modded: The same as everything else- go to a linear damping curve instead of the stock digressive curve.

44 0.20
44 0.20
44 0.20
20 0.30
44 0.20
44 0.20
44 0.20
44 0.20
44 0.20
44 0.20
44 0.20
40 0.20
38 0.25
36 0.20
36 0.25
36 0.25
36 0.25
34 0.25
30 0.25
26 0.25
36 5

The new stack has a much smaller crossover to reduce the low speed damping, and then added shims and a much larger pivot to stiffen the high speed.

It feels pretty extreme. Bouncing on the seat it almost feels like the shock is blown, but when riding it feels great.


The forks were giving me trouble at the Desert 100, but I'd had some time to play with the clickers so the software was able to duplicate the clicker changes I figured out. Basically, make the low speed damping like the clicker are open, and the high speed like they're closed.

Modded base valve:
20 0.12
24 0.12
24 0.12
24 0.12
24 0.12
12 0.12
24 0.12
24 0.15
22 0.15
20 0.15
18 0.15
18 0.15
16 0.15
13 0.15
13 0.15

I removed two low speed shims, added a 20mm face shim for some bleed, and stiffened up the high speed rebound stack. Sound familiar?

The new fork valving worked well on rocks, but I think it needs even more stiffening for big bumps and whoops. That'll probably be a mid-valve mod, but will have to wait until I get some actual riding in. All garage and no trail.......

Thanks!

That was with new springs, the revalved shock, but stock fork valves. Watching it was actually what motivated me to dig into the forks, as the front tire looked to me like it was extending slowly off all the bumps.

RE: the reservoir piston.

I'm just forcing it all the way in using air pressure, then releasing the pressure and installing the seal head letting the head's displacement force the piston back from the top of the cylinder. I think I got the idea from someone on this forum.

Seems interesting.. Let us know how it works!

So, more fork nonsense yesterday. I had swapped the fork springs back to stock, based on Vinduro's recommendation in his thread. That was mostly better, but the bike dived into whoops and waterbars even more than before. I tried to fix that with the midvalve. The float is much higher than on other bikes. It was around 0.65mm, though I couldn't measure it very accurately. I added an 8x10x.15 shim to the bottom of the midvalve to get the float down to .5mm. Full fork disassembly just to add a single shim. So it goes.

The new midvalve stack, with the 10x.15 that I added:


24 0.12
24 0.12
24 0.12
22 0.12
20 0.12
18 0.12
16 0.12
14 0.15
12 0.15
10 0.3
10 0.3
10 0.15
22 0.4


With one ride on it, I'd say it's an improvement. If I do anything more to it I'll probably reduce the float a little more to make it stiffer. A couple of points about that. One is that the rebound stack I'm using has a little bleed, which is also acting as bleed for the midvalve. The other is that I'm big and make mistakes. If I were lighter or could be sure that I'd always have my weight way back when hitting big bumps I don't think I'd need as much stiffness in the front end.

Are those KYB mid-valve pistons cross-drilled with a bleed hole? I've been working with my Marzocchi 50's to get rid of the dive, and more and more it's looking like the bleed hole in the MV piston is too large. It's certainly larger than I've seen on other forks. I may peen them closed a bit and see how that goes. I have not been in your model of KYB, though. Just thinkin' out loud here...

I couldn't see a bleed hole at all. And by the way that the forks reacted when closing the rebound clickers all the way, there isn't one.

What size is the bleed hole in the 'Zokes? I don't know how the flow numbers relate, but if you just calculate the area of the opening, a tiny amount of bleed or float around the shims is the same as a large bleed hole. FrEx, the 18x.1mm bleed shim on my rebound stack creates about the same open area as a 2.25mm hole. So reducing your midvalve float by .1mm would make an even bigger change than completely blocking off a typical bleed hole.

Yes, I see. Good point. I do have room to reduce float.

Another "related but different" problem is that bleed is bi-directional. Every time we move the clicker we change bleed on both compression and rebound. Very tricky to get the differential between C and R just right.

Finally had some time to get in those forks again...

It's a 2mm bleed hole and the float is currently .050" (kinda large!)