Zephyr (Kayaba) rear shocks repair/repack. Part 2.

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This time I decided to use new seal head instead of just seal replacement. This is not the most difficult  question as you know its dimensions. Zephyr 550 and 750 seal head dimensions are 12.5x36mm and as far as I see the many other Kayaba shocks, like ones from Suzuki GSX1400 or Kawasaki ZRX  have the same seal head dimensions.   I made a quick search of seal heads I may got as soon as possible and found out that it turned to be All Balls. I ordered a pair of seal heads and received them in week time.  The manufacture part number is 37-1012. The price is around 40$ per one seal head.

IMG_1729For this time I had shocks bodies cleaned and painted in the same shade of silver colour which I used for whole “Eight Ball” silver parts.  I forgot to give painter lower shock heads, but as I had all to assemble shocks I decided to left them in original  colour.  That’s how looks disassembled shock:

Kawasaki Zephyr 550/750/1100 kayaba shocks repir/repack/rebuildBut let’s assemble shock! Our first point  is to return all we removed from shock. New seal head, new damper rubber.

Kawasaki Zephyr 550/750/1100 kayaba shocks repir/repack/rebuildAs we removed lower head with rebounding adjuster, now we have to install it back. The main trick is to align biggest hole in adjusting rod

Kawasaki Zephyr 550/750/1100 kayaba shocks repir/repack/rebuildwith mark “1” on adjuster,

IMG_1853and screw rods of both socks on similar distance into the heads. Nothing difficult, but takes some mind concentration. Don’t forget to lock the head with lock nut.

Kawasaki Zephyr 550/750/1100 kayaba shocks repir/repack/rebuildI don’t like the idea to clamp shock in vise, so I invented my own little trick with  half of plastic bottle to place shock in it and rags to fix it there.  You do not need to apply much force while assembling shock, so system is stable enough for this purpose and rags which fix shock body also work like oil absorber.

Kawasaki Zephyr 550/750/1100 kayaba shocks repir/repack/rebuildAfter shock body is fixed in plastic can, we should fill shock with oil. This time I chose Fuchs Silkolene RSF 2.5W.

IMG_1894Then we may install gas reservoir,  push it into case and to install circlip.

IMG_1916To pull it back I used occasional Chinese valve cap and pliers.

IMG_1922Next step is shocks guts installing. Attention to Zephyr 550 owners! Do not forget install spring’ upper bearing washer on its place, because one may be unable to do so after piston is in the cylinder.

Insert the piston into the shock cylinder slowly. Push and pool it slowly few times to ensure an air absence behind  the piston.  Add oil into cylinder up to the upper circlip groove if needed, than slowly push the seal head trying to expel as much air as possible.

Kawasaki Zephyr 550/750/1100 kayaba shocks repir/repack/rebuildPush seal head dipper into cylinder and install both circlips.

Kawasaki Zephyr 550/750/1100 kayaba shocks repir/repack/rebuildPull seal head back by rod with piston. After that screw valve in gas reservoir and fill it with air to 0.1 Bar just to hold bladder being crumpled.

Then we may take shock from the can, position it vertically, and slowly pump it to get all the air above in the top of shock. The point is to pump slowly to avoid creating foam in oil.  After pumping, pull the rod back and  let shock stand vertical for some time (to dissolve foam if we got any).

Okay, we are close to finish. Our next step is  to get air and extra oil out of shock. For this purpose we use a pressure adjuster on top of the shock.

Kawasaki Zephyr 550/750/1100 kayaba shocks repir/repack/rebuildWe should unscrew this brass nut with improvised “special tool” like this:

IMG_1968Then carefully pull adjuster from shock case. Be careful and use a piece of rag  to catch potential oil splash.

Remove air valve from gas bladder and fill shock with oil up to the adjuster neck.

IMG_1997Install adjuster and fix it with nut. Now main work is done.

As you know from first part of this article, I prepared this shocks for my “Eight Ball” cafe-racer and I decided to add one little custom feature.  I designed and made a couple of custom brass compression adjuster heads.   To avoid any redundant external turn fixers I just soldered holding shelves right into heads.

IMG_1511 IMG_1505Bladders filled with air up to 8kgf/cm2 (yes, I am rather on side of “airists” in air VS nitrogen holy war )  and shocks  ready to spring installation.

Kawasaki Zephyr 550/750/1100 kayaba shocks repir/repack/rebuildAnd then shocks ready to be installed on the bike.

Kawasaki Zephyr 550/750/1100 kayaba shocks repir/repack/rebuildThat’s how my Yamaha XJ “Eight Ball” cafe-racer looks after this little update:

Kawasaki Zephyr 550/750/1100 kayaba shocks repir/repack/rebuild Yamaha XJ "Eight Ball" cafe-racer Yamaha XJ "Eight Ball" cafe-racerThe end.



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  1. Kozics Tibi

    What do you think about the k-tech repair kit:
    it’s compatible with seal head dimensions?
    Thank you!

    1. gazzz (Post author)


      Dimensions of Kayaba seal head is 36/12.5, and since description indicates that service kit is designed for KYB (Kayaba) seal heads, it should be compatible with original parts.

  2. manuel

    How much oil does each one carry and what price does it carry?

    1. gazzz (Post author)

      Hi Manuel,

      I bought 1l can of shock oil and it was more than enough, but I didn’t measure exact capacity of oil per shock.

  3. Piotr Kałuża

    Hi, where can I buy new damper rubber?

    1. gazzz (Post author)

      Hi Piotr,

      I assume that closest to you bump rubbers would be in Germany. Just copy phrase “Anschlagpuffer 12” into search line of German Ebay and choose “Motorradteile” category.

      Kind regards,

      1. Piotr Kałuża

        Thank you so much! And It is 12 x 25 mm?

        1. gazzz (Post author)

          Yes, 12x25mm would do.

  4. min

    Great rebuild info. I’m about to embark on a rebuild of Kayaba shocks for my SRX600 so will have this to hand.

    1. gazzz (Post author)

      Hi Min,

      This info might not be applied to original Yamaha SXR600 rear shocks. They look to be pretty different to Zephyr shocks.

      Kind regards,

  5. Mark Spreadbury

    Brilliant guide, my Zephyr 1100 Shocks are now in pieces awaiting Seal Kits. Thanks for sharing.

    1. gazzz (Post author)

      Thank you!

  6. arubi

    can you share your maked custom brass compression adjuster heads design


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