Honda CB 550 fork rebuild: Part 2

Honda CB 550 fork rebuild DONE!

Honda CB 550 fork rebuild DONE!

Well, I got back down to MotoPreserve and finished up the Honda CB 550 fork rebuild.  The result is hopefully smoother, more stable ride.  Based on the “oil” that came out of the forks, I would say this was LONG overdue…

The Honda CB 550 fork rebuild procedure…

The last thing I needed to do was replace the fork oil seal from the fork lower.  There is a specific indentation for it; make sure that the sides never get scratched since this will allow leaking.  I made sure to get the old seals out without and damage, but using a screwdriver leveraged against the top of the upper.  Then gently slipped the end under the seal and pulled up.  It came out quite easily.  I used the old seal to place on top of the new ones, with some oil around the seat, and tapped gently until they were seated.  A slight amount of oil on the inner surface of the new seal and the tube slid right in.

The final outcome produced a cleaner, slightly buffed fork lower.  Also, I derusted and sanded the uppers, placing a little WD-40 on them, to protect them from the elements.  This only needs to keep dry for a little while, since I will be removing them again this winter for the Steering Bearing install.  At that time, I will be removing the stock fork ears/headlight holder, and replacing it with an aftermarket one, with smaller fork caps at the body.

Fork Oil:

The most confusing part about this fix was determining the correct amount of fluid for these forks.  The CB550 manual says 160cc of oil for a dry filling (after rebuild), but the Progressive Tech Sheet mentioned that these springs displace more fluid, requiring less than stock.  I ended up going with the stock amount, hoping that I could drain a little if/when I determine that the amount is too little.

UPDATE: At the time I did this rebuild, I used ATF as described in the manual.  Since the time that these old classic bikes were built, newer (and arguably better) fork oil has been developed.  These “new” fluids come in a variety of weights to help with the tuning of the front suspension.  Although I have used some very expensive brands as a test, I most often turn to affordable Maxima Fork Oil, which can easily be purchased on Amazon.  Please comment below if you find a different fork oil you’ve had good experiences with. (MotoPreserve may get commissions for purchases made through links in this post)

Unfortunately, this was not a full how-to, since I was moving quickly to get this done.  If anyone has any questions, please feel free to ask.

You can see more about the rebuild and restoration of the Honda CB550 HERE:

4 Replies to “Honda CB 550 fork rebuild: Part 2”

  1. What kind of oil did you use in your fork rebuild? Service manual recommends ATF but I see some folks running different weights. Curious what your experience here has been.

    1. I actually used ATF like the manual states – but there are far more fork fluids on the market since that manual was published. When I rebuilt the FZR forks I used a fancy motorcycle fork oil – but I can’t recall the name now. It comes in far more weights than would be found at an auto parts store, and also had a very helpful, flexible nozzle for pouring it into the forks… But you pay the price. I think the bottle, which filled the FZR forks with a bit to spare, was $15!

      1. Thanks for the response, Scott. I’m due for my 1976 CB 550’s first service interval (only 5400 miles when I got the bike!) The details you provide on your blog are very helpful and I will refer back regularly. Keep up the good work.

        1. I really should post the whole 3000 mile tune-up procedure. It is definitley something worth having in print – so that you can reference while going through the steps. Good luck, and let us know if you have any question, and send us a photo of your bike!

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