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