Reworking Sachs shock ...

Thinking about the valving changes and had a crazy idea ... this picture shows the rebound stack side ... during compression, oil flows thru those scoops cut out in the piston, so it is partially blocked by the rebound shims.

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So I'm thinking, I should remove that largest rebound shim, the 38mm.  That will make rebound lighter (faster) and it would allow more oil to flow thru the piston on compression.  This would help high speed compression IF the problem is not enough oil flowing through the piston.  It will not help if the issue is mostly with the compression shim stack.

The reason I say this is crazy ... rider says "Hey, I need to reduce my high speed compression damping" ... suspension guy says "Sure, let me pull that thar big ole shim off the rebound side"     (In this case I am both the rider and the crazy suspension guy)

And then I'm wondering if I should double down ... remove that thar big rebound shim and also make a change on the compression shim side.  Hummm ...  

Adding some logic? and reason? to the crazy plan, I should just remove the largest rebound shim.  Already making a number of changes:  stiffer spring, different shock oil, probably higher nitrogen pressure ... not sure I want to make 2 shim changes with this round.  

Gotta do some    

Reservoir wrap up time ...

One option was to drill our flat reservoir cap, tap it, and screw in a schrader valve.  Sounds reasonable enough and low cost.

But ... there isn't room.

Schrader valve size ...
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Clearance on bike ...
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It would not fit.

There is an option that some KTM dirt bikes have ... they have a valve where you insert a needle.  That would be the same idea, drill our flat cover, tap it, screw in that needle bolt/valve.  This looks like what Traxxion Dynamics did in the early picture that was posted.  I didn't really want to go that route.  

The Racetech option I showed earlier is an "High Volume" cap, so it would stick out a lot more, so I skipped that one.

Found this one, called a "Elka Reservoir Cap - 46mm"
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Bought it from Hygearsuspension and it fits perfectly!  Seems like it is from an ATV/four wheeler shock.

Here it is installed:
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Here is a pic of the GSXR spring I got ... red one is stock, yellow one is from the GSXR shock:

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For putting this all back together, I really liked this info I found from Race Tech:  http://www.racetech.com/PAGE/TITLE/IP%20SK%20Rebuild%20PISTON%20RESY

In those steps we have the "Open End Reservoir" so skip the "Closed End Reservoir" parts.  Also no need to read the "Seal Head" stuff, just ignore that.

So the first step is getting the piston out of the nitrogen reservoir side.  Hum, it was all the way in, nothing to grab on to and pull it out.  Snap ring pliers can't reach it.

What to do.  Figured I needed to put some air pressure in the other side to blow (push) it out.  
And lucky lucky, that chamber is also ~46mm, so the Elka reservoir cap for the nitrogen side also fits over on the shock/oil side!  

So I pushed the Elka cap into the shock chamber, put in the clip, got my mountain bike shock pump and slowly added air ... and that pushed the piston out of the nitrogen side.  Success!  Whew, got lucky that those two chambers are both 46mm.

Some pics of what I'm talking about:  

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Then, following those Race Tech steps ... you fill up the nitrogen side completely with oil, and press that piston back in place ... so did that.

I then opened up that bleed screw on the shock body ... pushed the nitrogen side piston in a bit more ... oil flowing out the bleed ... then tightened up that bleed screw.

Then push the nitrogen piston all the way in.  This has pushed the oil through and into the shock chamber side.  And when looking into the nitrogen chamber you see that piston all the way in (so it is an empty chamber at this point).

Install the Elka cap into the nitrogen side, push it in, need to push a bit, release some air, push some more, release some more air, continue until that cap is past the clip grove in the body.  Put the clip in place.

Then put in 20-40psi of nitrogen gas.  (OK, I cheated, and used my mountain bike pump again)

Whoops ... messed up the steps a bit here.

Backing up in time ... getting the shock valving ready.

So I decided to double down on a "fix" for the high speed comp issue.

I removed the largest rebound shim ... idea here is that will allow more oil to flow during compression (shim not in the way) ... and if that lightens up rebound, that's ok as that was a need/goal too.

On the compression side I removed the 18 x .2 shim.

Put all the washers, shims, piston, shims, washers in place.  Wee bit of blue loctite and put the bolt back on.

I did all that before messing with the reservoir.

Ok, so I had the shock guts prepped ... and the reservoir side done ...

So I filled up the shock side to about 10mm from the top.

Put the piston bushing on and gently worked that into the shock.  And pushed everything in, slowly pull it back out (but leave all that valving stuff in the oil), then press it back into the oil again ... do that 3-4 times to remove any air.

Then top the shock body 100% to the top with oil, and then press the last part into the body.  Yes this is messy and oil overflows down the side of the shock.  

As the rubber o-ring gets inside the shock body, you can't press any more ... you have a shock full of oil and 20-40 psi of air on the other side pushing that piston back.

So you press the schrader valve a wee bit ... then push the shock guts in another 2-3mm ... press the schrader a wee bit ... press another 2-3 mm, etc.

Do this until the shock guts are in beyond the clip grove.  Insert the clip into the grove.  

Then you are ready to put full pressure in the shock.  Pump it up to 180 psi.  

Then push the aluminum dust cover back in place ... tap it in with a rubber mallet, pretty soft metal and it is just a dust cover so easy taps to work it into place.

So then I had this:

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I put on the GSXR spring ... got my ratchet tie down strap hooked up again ... was way harder getting this on vs. getting the stock one off ... it is 5 mm longer and a stiffer spring.

If I was going to do this more often I might have to buy or rig up a spring compressor.

And ... ta da!  

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As a refresher, the shock I've been working on came from woodrow53 .  This allowed me the time to investigate all this stuff and still have my GRiSO all together and available for rides.  Thanks again for this!!

So shock all together I walk over to my GRiSO ... huh, how do I get the shock off.  

I have read a bit about this ... pulling off the airbox and a bunch of stuff ... oh well, time to read up some more on this.  

And also, my first time with this was a lot of learning and discovery ... if you handed me a stock shock now (with spring and reservoir cap), it would be very easy to pull it all apart and get it back together again.  

Oh ... price breakdown so far ...

$12 - oil
$25 - spring (ebay, GSXR shock)
$30 - Elka reservoir cap

$67 total

Great read, worthy of a stickie. Would like to do this while my stocker is out

On removing, jack up the belly, secure front and remove from bottom. Good Time to grease bearings and spline. There’s a good pic in one of Pete’s threads.
Iirc, topside is covered in the manual

14MM hex needed

Whoops ... I clicked on the + - things while looking at your post ... looks like that was a negative vote? Sorry about that!!

I up (+) voted him, somebody else want to regain the balance?

Added a bit but not enough to restore the green balance. NEXT!

happy to help, great post too!.

Man, removing this shock, wow, wasn't ready for this challenge.

So to warm up, I pulled these out and once I could solve each one I knew I was ready to go back into the garage and work on the GRiSO shock removal challenge.

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So I read about the "remove it from the bottom (RFB)" approaches, and the "remove it from the top (RFT)" ones.

I like the from the bottom better, and started out going that way, RFB.  When I hit my first snag, I switch to RFT.  Then hit a snag that seemed more of a pain than the RFB snag, so switched back to RFB.

Then hit a snag, repeat, repeat, repeat.  Whew.  

I can see that RFB with the left side plate off would be a winner ... but ... my stand lifts the bike from the side plate bottom bolt.

So finally, just like those little metal puzzles, the shock came out!  I really have no idea how it finally happened, just the right twist, lean, twirl, something.  RFB was the winner for me.

Putting my rebuilt shock back in place was equally puzzling ... just lots of metal puzzle play and somehow it got in there.  

While I was doing this I decided to grease up all the shock linkage bearings ... wow ... glad I did.  I've probably seen 37 posts from Roper saying to grease this up, and he is 100% right, there was really no grease in there.  

I didn't have the mental energy to do the swingarm bearings at this time ... but I will be going back for that in the future.

Now on to preload setting ... for wording, I like "bike sag" and "rider sag" as it makes sense to me ... some call this "static sag" and "race sag", but I ain't racing.  

I had read many versions of the "right" thing to do, here are 4 I found:

Source 1 - Bike sag = 11mm;  Rider sag = 27-33mm
Source 2 - Bike sag = 10mm;  Rider sag = 30-35mm
Source 3 - Bike sag = 3-5mm; Rider sag = 33-35mm
Source 4 - Bike sag = 10mm;  Rider sag = 30 mm

So I ended up with Bike sag = 10 mm, and Rider sag = 29mm

This is an indicator to me that the spring is a bit stiff ... if I was a bigger guy it would sag more than 29mm when I got on it ... but that is very close to these difference suggestions.

Ahhhh, test time!  And off I go ...

First thing, rebound is much faster/lighter than stock.  And that was a goal.  And that should be the case, stiffer spring, largest rebound shim removed.  

So I went to 10 clicks out on rebound (vs. before I was around 25 clicks out).

Ride was still very firm, spring felt too firm.  I went to 2.5 turns out on compression.

Rode some more ... still some high speed hit happening, much much better, but still there.  Small ripple bumps were very nice, kind of float-ie.  

As I rode more I liked it better & better.  Ride is still on the firm side, but the GRiSO is a beast-o, so I don't want it cushy cushy and then not be able to handle a faster pace.  

I also realized that in "test mode" you try to run over everything and evaluate each bump
So I got out of that and just rode it another 15 minutes like a normal ride, very nice.

Then I headed over to where I knew there were 2 sharp bumps in a row, 45 mph road ... headed for the sharpest/tallest part of the bumps ... and it did not magically float over them as if they weren't there, and actually I don't think a Matris/Mupo/Ohlins would float over them either ... but it really wasn't bad.  The sharp jolt did not happen ... no hammering from the seat ... yes, I felt them, the bike hit some bumps, but way better than stock.

So now I have my stock shock off the bike, sitting on a work bench.  Do I go for a round II?  Not sure.

If I did a Round II, I think I would:
1. Leave the 38mm rebound shim in
2. On the Compression side, switch out 3-5 0.2mm shims with 0.15mm shims
3. Get a spring between the stock 8.2 and this 9.5

In the meantime, I will work on those metal puzzles to keep my shock removing skills honed.  

Great write up

But if you haven't been in to grease up the swinging arm bearings, to get it to perform as it was designed, aren't you being a bit premature in setting up the shock ?

You're diving in & tackling stuff that is above my pay grade. So the swingarm will be easy for you, just hoist it up from the garage roof & the sideplate can come off.

Then getting the shock in & out is simple.

Cheers

Nobleswood wrote:

Great write up

But if you haven't been in to grease up the swinging arm bearings, to get it to perform as it was designed, aren't you being a bit premature in setting up the shock ?

You're diving in & tackling stuff that is above my pay grade. So the swingarm will be easy for you, just hoist it up from the garage roof & the sideplate can come off.

Then getting the shock in & out is simple.

Cheers

Well, the bike has < 1000 miles on it.

I'll get the swingarm bearing by 2000 ish miles or sooner. I'm a bit afraid of the CARC & drive shaft.

usedtobefast wrote:

Whoops ... I clicked on the + - things while looking at your post ... looks like that was a negative vote?  Sorry about that!!  

No worries and thanks guys. Happy new year!

I’ll try the puzzle next time. Swingarm removal wasn’t too challenging. Was surprised at its weight.

Excelent reading, thanks.

Adding something, just to make this post "everything about the Sachs shock":

My bigest issue was the preload.
The spring is perfect for my ~70kg, having passenger and baggage, bottomed hard on bumps, had to change the preload, and that was an issue.

Solved it by installing this:
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Its length, retracted, is 34mm. Fully expanded (24 clicks) is 42,5mm.
Before instaling it, I measured the distance from the top of the spring to the shock head - was 28mm (sag adjusted for solo riding). Had an other bottom spring retainer machined, 6mm shorter thatn the original.

Now, changing preload from solo to full load, needs less than a minute.

Update after a bit more riding ...

So things are certainly better than stock, glad I've done this so far, but I'm going for a Phase II on the shock.

I went too stiff on the rear spring I believe. Stock spring is 8.2 kg/mm, and I went to a 9.5 kg/mm. To me, I feel like the rear is sprung stiffer than the front (stock springs). It is kind of nice that the rear is held up higher, probably benefiting from a more gentle leverage ratio, but the bike just feels a bit off to me with the rear being stiffer.

Also, the high speed comp is still a bit abrupt, still more hit getting to me than I'd like.

So plan is:
1. Get a spring between the stock 8.2 and the 9.5 I have
2. Leave the 38mm rebound shim in place
3. Go to thinner shims on the compression side

Springs springs springs!  

So, following my "it's gotta be cheap" philosophy ... I went back to my compatibility chart ... some interesting info:

{disclaimer I: this is all based on info from racetech}
{disclaimer II: at some point a higher rate spring might be too thick to fit}

9.1 kg/mm 2008-2010 Kawasaki ZX1000 Ninja ZX-10R
8.3            2006-2007 Kawasaki ZX1000 Ninja ZX-10R
10.7          2002-2003 Kawasaki ZX1200 Ninja ZX-12R
11             2000-2001 Kawasaki ZX1200 Ninja ZX-12R
9.7            2006-2011 Kawasaki ZX1400 Ninja ZX-14
9.2            2007-2008 Kawasaki ZX600 Ninja ZX-6R  
9.9            2005-2006 Kawasaki ZZR 600
9.4            2006 Suzuki GSX-R600
9.5            2006 Suzuki GSX-R750
8.6            2004-2006 Yamaha YZF-R1
8.8            2002-2003 Yamaha YZF-R1
8.0            1998-2001 Yamaha YZF-R1
9.8            2006-2007 Yamaha YZF-R6
10.8          2005 Yamaha YZF-R6
9.85          2003-2004 Yamaha YZF-R6

So I liked the 8.8 kg/mm spring for this go around ... 2002-2003 R1.

Off to eBay, entire shock for $35, spring looks good, buy now.  

And I'll hope that shock has the thinner shims I need!  

So Phase II underway!

Be careful I went down that road lookig for springs for my tuono, CBR1000xx springs should have done it but turns out the stock Honda springs were rising rate and also too long to work with the spacers I had...