Master Cylinder Rebuild: 1973 Honda CB500

Rebuilding the master cylinder on a 1973 Honda CB500

Motorcycle Classics staff
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CB500 Brake Master
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This is what our CB500 brake master cylinder looked like after removing it from the bike. Removal is straightforward, requiring only that you disconnect the brake line from the master cylinder after either draining the fluid out through the brake caliper bleed screw or by sucking the fluid out with a vacuum pump.
MC Staff
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This rebuild came about as part of Project Café, the 1973 Honda CB500 Four we’ve been morphing into a street café racer with help from BikeBandit.com. We covered rebuilding the brake caliper in the September/October 2009 issue, a project you can also find here on our website.

Although this particular rebuild deals with the master cylinder from our ’73 CB500, Honda used basically the same master cylinder (and caliper) on just about every disc brake-equipped Honda starting with the CB750 in 1969 up until about 1978, when they started making significant changes to their hardware, although the GL series used a different style master cylinder and caliper. As with any project like this, we highly recommend having a manual on hand to help guide you through the process and to give you exploded images of parts so you can better understand how they all go together. Pay particular attention to cleanliness. You don't want to contaminate the brake system with any dirt, grease, water ... anything. Brake parts cleaner is cheap: use plenty of it as you work along and allow plenty of time for parts to air dry before moving on. Use brake fluid as a lubricant when you're honing the cylinder bore and when you're putting internal master cylinder parts together and into the master cylinder bore.

The image gallery will take you through our rebuild step-by-step. And don’t forget, if there are issues we’ve neglected to point out or tips you can add to our rebuild, just use the “Comments” feature to add your input to the discussion. – Richard Backus 

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Archived Comments

  • James Slater 9/10/2011 10:53:08 AM

    The rebuild is straight forward and I love your idea for a cylinder hone. However; I do have a question about it. On the cylinder there are two holes in the cylinder I know one is bleed back and one is to push the fluid. My question is are both holes open to the bore? I have a cylinder almost exactly like this from a CB400A and my problem is the bleed back hole doesn't go through to the bore. Is it supposed to? are both of your cylinder holes open to the bore? Please let me know as this would be helpful for other owners of these master cylinders. Thanks,

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