1985 RZ350

RZ350 - Front Caliper Overhaul

The front calipers on my RZ350 are the single caliper floating type. This means they have a single caliper and pad on the outboard side of the disk rotor, and a static inside pad. The entire caliper can move on its mounts so when the caliper applies force the the disk, the static pad is pulled agianst the inside of the disk rotor as the caliper moves on its mounts. Later RZ350 models had calipers from either side similar to the rear brake caliper.

To remove the caliper from the forks, remove the two retaining bolts that hold it in place. I still had my hydraulic lines conected when mine were off the bike which was a mistake. It is much easier to remove this connection when the calipers are in place. If your hydraulic system is not empty be sure to have a small dish or jar to drain to when the lines are removed.

On the outside face of the caliper find the single Allen head bolt which retains the brake pads. Loosen it fully and start to remove it from the casting.

As you remove the pin, the disk brake pads will slide free of the caliper.

There is also a metal anti-rattle piece which fits in behind the brake pads. This can be saved for the rebuild.

The mount can be removed from the main caliper body. It is simply a friction fit but may be a little stiff because of the grease. Have a look at the little rubber boots at the end of each peg to see if they can be reused.

Be sure to save the thin metal plate which attaches to the fork mount. This can be reused in the rebuild.

The caliper now needs to be forced out from the caliper mount. The only way to do this effectively without damaging the caliper is to blow it out with compressed air. Make sure the bleed valve is tightened down and use a rag over the caliper to stop it from shooting across the garage floor. You can use a compressor which is best, but a foot pump can also work well. Put the air nozzle into the hydralic line hole and a few short blasts should set the caliper free with a loud pop.

The master cylinder piston is located beyond the lever mount. Remove the small rubber dust cap and you'll see the end of the piston and the circlip that retains it. I found that getting the circlip out with circlip pliers was almost impossible becuase the end holes were partially hidden in the groove. I knew I had a second (new) circlip in the rebuild kit so I managed to hook one end of the existing one and just pulled...

..and it finally came out but was not able to be reused. At this point the internal spring in the piston will push the pison parts out of the casting.

Remove them from the casting but keep good notes on the order in which they need to be reassembled. First is the spring, then a rubber cap, then the metal piston casting with a rubber seal around it.

The rebuild kit from Yamaha contains all new rubber parts, a new metal piston casting, a spring, and a new circlip.

The new seal needs to be installed over the metal piston casting in the direction shown. I found the easiest way to do this was to slide it over the small end (to the right above) and then stretch it over the first ridge.

Build the parts up in the same way that the old ones were removed. Use a little clean hydraulic fluid to lubricate the seals.

Insert the entire assembly into the master cylinder housing. I sanded down the casting with steel wool and refinished the metal with special casing paint. If you do the same, be sure to tape off all holes and openings to keep paint out of the working areas.

Push the piston assembly in and refit the new circlip. This is easy to do with circlip pliers because you can get access to the clip ends but these become partially hidden when installed. Finally fit the new dust seal and refit the single small lever spring.

Refit the lever with some grease around the pivot point and the point where the lever makes contact with the end of the master cylinder piston. Tighten the pinch bolt and refit the brake switch if it was removed during the rebuild.

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