SHOCK SHIM STACK TUNING - Yamaha XTZ1200Z Super Tenere 2015 -

Discussion in 'Land of the Rising Sun: ADV Bikes from Japan' started by Xfool, Aug 24, 2017.

  1. Xfool

    Xfool Been here awhile

    Joined:
    Jul 21, 2005
    Oddometer:
    450
    Location:
    Thousand Oaks, CA
    Tenere shock failure
    My Tenere shock blew-out riding 2-up through Death Valley. No doubt the shock works harder riding 2-up. On-the-other-hand, we weren’t exactly “airing it out” in the national park either.
    1-blown-band.png
    The shock didn’t blow oil, it just quit working. The cause was a blown piston band and it blew on the rebound stroke. So it wasn’t a hard hit that caused the failure.

    The shock has some kind of molded on piston band deal. Replacements may not exist – at least I can’t find one.
    #1
    Hoak likes this.
  2. Xfool

    Xfool Been here awhile

    Joined:
    Jul 21, 2005
    Oddometer:
    450
    Location:
    Thousand Oaks, CA
    yzf600 replacement shock
    The first though was replace the shock with something out of a dirt bike. But the longer shaft strokes on those shocks make the shocks way too tall to fit in the Tenere.
    2-yzf600-00-shock.png

    A yzf600 street shock turns out to have the same 70 mm stroke and the same mounts. The eye-to-eye length is about 10 mm longer and might be made to work by hacking the Tenere link arms. Sourced a yzf600 shock out of ebay junkyards for $40 to figure out if it could be made to fit the Tenere.
    #2
    Hoak likes this.
  3. Motociclo

    Motociclo Without motion, nothing.

    Joined:
    May 18, 2017
    Oddometer:
    426
    Location:
    Straya!
    You could probably change out the piston completely. Looks like the S10 is a Soqi shock.
    I'm not sure what size your S10 shock is, I know that the yzf shock you have is a 40mm. They do have replaceable piston band. Locates better than one on S10 shock.
    Absolute prick to get apart though.
    #3
  4. Xfool

    Xfool Been here awhile

    Joined:
    Jul 21, 2005
    Oddometer:
    450
    Location:
    Thousand Oaks, CA
    ... yzf600: prick to get apart. :becca

    Been following your posts:
    Africa Twin CRF1000L suspension; CRF1000 shock rebuild; CRF1000 fork revalve
    Good to see some rider suspension tuning info, but wrong bike. Need to hack out something for the Tenere.

    The Tenere shock was easy to get apart. After venting the gas charge - an adventure in itself we'll get to latter - the shock was easy to disassemble: Push the seal head down with your thumb, pull the snap rings and you are done.

    The yzf600 shock was trickier. The seal head on the yzf600 shock is tightly wedged between two snap rings. To pull the snap rings you have to clamp the shit out of the shock, hard enough to crush the top out bumper and push the seal head down far enough to make room for pulling the snap ring. That took a wood working “pipe clamp” and a hacked 1/2” pvc coupling to get enough crush on the seal head to pull the snap ring.
    #4
    Hoak and Motociclo like this.
  5. Motociclo

    Motociclo Without motion, nothing.

    Joined:
    May 18, 2017
    Oddometer:
    426
    Location:
    Straya!
    Cheers, if i end up with a S10, will piece something together!

    YZF shock was the one i meant was tricky.
    Most shocks very easy.
    #5
  6. Xfool

    Xfool Been here awhile

    Joined:
    Jul 21, 2005
    Oddometer:
    450
    Location:
    Thousand Oaks, CA
    yzf600 shock guts:
    3-shaft-assbly.png
    #6
    Hoak likes this.
  7. Motociclo

    Motociclo Without motion, nothing.

    Joined:
    May 18, 2017
    Oddometer:
    426
    Location:
    Straya!
    Did a similar type thing.
    Makes it fun!!!!
    #7
  8. Xfool

    Xfool Been here awhile

    Joined:
    Jul 21, 2005
    Oddometer:
    450
    Location:
    Thousand Oaks, CA
    Tenere valve port geometry
    Dig around on the net and there is a bunch of info on shock tuning. But one of the rarest things that is nearly impossible to find is a photo of a stock shock piston.
    No idea why that is so hard.

    YOU ARE ABOUT TO SEE SOMETHING THAT NOBODY AIN'T NEVER EVEN SEEN BEFORE!
    -- SO GET READY!! --

    4-tenere-valvesS2.png
    Turns out the Tenere valve ports are identical to the yzf600 shock. Soqi snowmobile shocks look pretty close as well. Port dimensions in the table were set to give the rectangular port geometries in Shim ReStackor the same port center line and flow area as the round ports on the Tenere valve.

    Motociclo has a hot tip: Soqi 40mm snowmobile valves look pretty close. Hy gear suspension has them. No idea if they fit or not.
    4a-soqi.png
    #8
    Hoak and Motociclo like this.
  9. Motociclo

    Motociclo Without motion, nothing.

    Joined:
    May 18, 2017
    Oddometer:
    426
    Location:
    Straya!
    Nice work. Good to get a result. Using ReStackor I see.
    Couldn't see why snow mobile piston wouldn't fit. If it use 12mm ID shims, I would say it will be a direct swap. Makes parts supply easier also.
    #9
  10. Xfool

    Xfool Been here awhile

    Joined:
    Jul 21, 2005
    Oddometer:
    450
    Location:
    Thousand Oaks, CA
    Tenere piston band fix
    The initial idea was use the yzf600 shock as a replacement for the Tenere. But, the steel body on the yzf600 shock turns out to be slightly smaller than the aluminum Tenere shock. There is no easy way to adapt the Tenere spring preload adjuster to the smaller yzf600 shock body. Losing the preload adjuster was a deal breaker for me so I abandond the yzf600 shock as a replacement.

    But - as luck would have it - the yzf600 shock piston bolts right on to the Tenere shock. That was unexpected since the yzf600 uses a 12.5 mm shaft and the Tenere has a 14 mm shaft. Anyway, it bolts on and the port geometry is identical. The only difference is the yzf600 piston uses a removable/replaceable piston band and frankly that is a feature.

    The fix for a blown Tenere piston band is get a piston out of a yzf600 shock. Simple.

    The SOQI snowmobile shock piston might work. Before jumping on that the port dimensions on that valve need to be checked to make sure they are close enough you can tune around any differences. And check the valve thickness. The KYB catalog shows a couple different thicknesses for that valve and that is going to effect how many shims you can stack on before running out of shaft. It may well be identical – Don’t have one – Don’t know.
    #10
    Hoak and Motociclo like this.
  11. Motociclo

    Motociclo Without motion, nothing.

    Joined:
    May 18, 2017
    Oddometer:
    426
    Location:
    Straya!
    I just so happen to have a KYB valve laying around. Width comes in at 18mm, compared to 13.3mm for the yzf valve.
    Total shim stack thickness isn't real thick, 3mm total for comp and rebound, so may have to use thinner spacing washers.
    If you revalve, stack thickness will only increase. KYB will flow more the Soqi valve, would need stiffer stack to suit at a minimum.
    The Soqi snow mobile shock valve might be a closer option.
    #11
  12. Xfool

    Xfool Been here awhile

    Joined:
    Jul 21, 2005
    Oddometer:
    450
    Location:
    Thousand Oaks, CA
    Replacement Valves
    Measured a valve thickness of 13.5mm for the stock Tenere, same for the yzf600 shock. Replacement valves 5mm one way or the other may seam like no big deal when measuring. But, 5mm is equivalent of fifty 0.1mm shims and that’s a boat load.

    Unfortunately Yamaha didn’t leave much room for hacking around. One mm one way or the other is a big deal.
    4-tenere-valve3.png
    You can get a yzf600 shock out of a junkyard for $40. It’s an easy fix and you’ll get a handful of valve shims out of that junked shock to hack around with.

    RaceTech might be another option for a valve. Last time I checked there recommendation was replace the shock with one of their own: RT G3-S piggyback reservoir; $1349.99

    Feel like that gives me license for a whole bunch of hacking around trying to fix this thing.........
    #12
    Hoak likes this.
  13. Xfool

    Xfool Been here awhile

    Joined:
    Jul 21, 2005
    Oddometer:
    450
    Location:
    Thousand Oaks, CA
    Spring Rate
    The first step in suspension tuning is get the right spring rate. Other ADV threads have lead the discussion on the Tenere being seriously under-sprung and I agree. RaceTech recommends a 17.8 kg/mm spring for my weight. That is a 32% increase over the stock 13.5 kg/mm spring. Installing the 32% stiffer RaceTech spring gives me 2.5 inches of race sag (33%) with 6 clicks on the preload adjuster – perfect!
    #13
    Hoak and Motociclo like this.
  14. Xfool

    Xfool Been here awhile

    Joined:
    Jul 21, 2005
    Oddometer:
    450
    Location:
    Thousand Oaks, CA
    Rebound tuning for stiffer spring
    Damping wise I was pretty happy with the stock shock. The spring was too soft, but the suspension was nicely damped imo. To keep that performance I want to weight scale the stock damping to the 32% stiffer RaceTech spring. Weight scaling math is pretty simple – Damping needs to increase by the square root of the spring rate change. That works out to a 15% damping increase for the stiffer RaceTech spring.
    5-weight-scale.png

    The trick in tuning suspensions is getting the right high speed damping to control the wheels, the right low speed damping to control the chassis and the right transition between the two so the shock works everywhere across the speed range. Yamaha worked all of that out setting up the stock Tenere suspension. Weight scaling preserves that factory tuning by simply scaling damping to correct for the change in spring rate.

    The other approach is scale something out of another bike. If you had the hot setup for a crotch-rocket or dirt bike you could scale that over. That gets more involved taking into account differences in weight, spring rate and link ratio. Wouldn’t want a crotch-rocket setup but a dirt bike setup scaled to the Tenere might be good.

    But Yamaha knows what their doing. The scaled stock damping is good enough as a baseline and the bike can be further tuned from there.
    #14
    Motociclo and Hoak like this.
  15. Motociclo

    Motociclo Without motion, nothing.

    Joined:
    May 18, 2017
    Oddometer:
    426
    Location:
    Straya!
    Be mindful when using the weight scale, if your rebound damping was weak with stock spring, after weight scale it will be still weak.
    ReStackor weight scale doesn't take into account weak valving. Just proportionally scales up damp force. I used weight scale as a start point, but that's all it was good for.
    I had to double rebound damping on Af Twin shock, comp damping I think was only about 25%. That was only going from a 8.3kg up to 9 kg spring.
    When I went to a 9.8 kg spring, I had to up rebound damping considerably more again, but left comp damping alone.
    Your comp valving although important, is less critical. The comp damping is largely controlling unsprung mass, so the forces are less. Even with high shaft velocities.
    The correct spring rate will help comp side of things considerably. I tend to go for stiffer spring, lighter comp damping.
    #15
    Hoak likes this.
  16. Xfool

    Xfool Been here awhile

    Joined:
    Jul 21, 2005
    Oddometer:
    450
    Location:
    Thousand Oaks, CA
    Stock rebound damping
    The stock Tenere rebound shim stack uses a 29.25/26.15 ring shim to preload the stack, aka a split ring shim. Preload from the ring shim holds the stack closed at low speed forcing all of the shock fluid flow through the clicker circuits. That increases low speed damping.

    Damping force wise the Tenere generates about 115 lbf-s/in of damping at 5 in/sec. That high damping force at low speed is needed to control the chassis. After the shim stack cracks open the damping force falls to around 40 lbf-s/in at shaft speeds above 25 in/sec. That loosens up damping at high speed to allow the wheels to float over bumps.

    6s-stock-rebound.png
    Weight scaling to the stiffer 17.8 kg/mm RaceTech spring needs a 15% increase in damping force across the entire speed range. That 15% target is shown by the dashed orange line and is basically equivalent to running the stock shock with the clickers fully closed.

    Closing the clickers gets high speed right, but at low speed (0-5 in/sec), the closed clicker curve generates way too much damping and that will cause the suspension to pack. Getting the damping force curve right across the speed range is going to need some mods to the shim stack.
    #16
    Motociclo likes this.
  17. Xfool

    Xfool Been here awhile

    Joined:
    Jul 21, 2005
    Oddometer:
    450
    Location:
    Thousand Oaks, CA
    The 115 lbf-s/in rebound damping on the stock Tenere at 5 in/sec is about two times stiffer than the dyno data Teknik motorsport shows for the Africa Twin. And that was for running the Africa Twin shock at 5 clicks!

    Gives some credibility to Motocyclo’s need to double rebound damping on the Africa Twin. On the other hand different bikes, different link ratios, etc...

    You can check to see if rebound damping is "way off" by looking at the chassis suspension response zeta values. By suspension tuning "rules of thumb" the usual target for low speed chassis damping is zeta values around 0.7. That typically pushes the lighter weight of the wheels into an over damping condition giving zeta values in the 1.0 to 1.2 range. Tenere rebound damping by my calcs is a little bit on the over-damped side at low speed and I think Yamaha did that on purpose for fire road drifting.
    #17
    Motociclo likes this.
  18. Motociclo

    Motociclo Without motion, nothing.

    Joined:
    May 18, 2017
    Oddometer:
    426
    Location:
    Straya!
    S10 link ratio 2.71.
    Af Twin link ratio 2.31.
    Higher link ratios always require higher spring rate, with out factoring in weight of bike.
    Big spring on tenere needs plenty of rebound for sure.
    1200kg of spring force at full comp. Takes some reining in.
    The split shim on tenere is digressive. Preloaded shims good at minimising total shim stack. Higher initial damping force, due to preloaded shims.
    Digressive works well on comp stack to control low speed weight shift such as braking etc.
    0.7 is an ideal target for bikes. Good trade between performance and comfort.
    Check a shock dyno graph out and you can see the transition from low to high speed, called "the knee", the zeta value may go from 0.7 down to 0.4 for example. Makes high speed less harsh and more compliant.
    Some good info coming from you Mr Xfool.
    #18
  19. Xfool

    Xfool Been here awhile

    Joined:
    Jul 21, 2005
    Oddometer:
    450
    Location:
    Thousand Oaks, CA
    Tenere link ratio
    After I got the spring off the shock I reinstalled the bare shock and took some measurements of shock versus wheel position. Race sag is at 2.5 inches and the shock hits the bottom out bumper at 5.5 inches. To arrive at the spec’d 7.5” of wheel travel the last two inches of stroke crush the bottom out bumper to zero thickness by my measurements.
    x12-link-ratio.png
    The link ratio at race sag on the non-ES Tenere is 2.85. Most dirt bikes run link ratios right around that same value of the non-ES Tenere.
    #19
  20. Xfool

    Xfool Been here awhile

    Joined:
    Jul 21, 2005
    Oddometer:
    450
    Location:
    Thousand Oaks, CA
    ES Tenere link ratio
    The electronic suspension on the Tenere ES has the same suspension travel but uses a different shock with an 89mm stroke compared to the 70mm stroke on the non-ES. Karlxx shows the spec differences in stroke and spring rate for the two bikes.

    With the longer shock stroke the ES link ratio is going to get pushed down somewhere into the 2.1 range at race sag. The Af Twin link ratio more-or-less lines up with that.
    #20