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Discussion Starter #1
My rear brake pedal seems to go down further than it use to and when I pump it 2 to 3 times it is where it use to be. I have checked the rear brake pads and they are good and at the rotor, so that is not the problem. I think I need a new rear master cylinder. Can I change it out and just bleed the rear brake? Which brake fluid, DOT 4?
 

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Yes, these bikes use DOT-4. If your pedal is mushy and pumps up, then the problem is likely air in the lines.
How long has it been since you've flushed the brake systems. If it's been longer than (I think) 24 months, you should do that first.


Then, you'll need to bleed all the air out of the lines. There is a special addition to the OEM bleed procedure called the Rocky bleed. Just search for that on this forum and you'll find lots of hits showing the details.


Good luck.
 

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My rear brake pedal seems to go down further than it use to and when I pump it 2 to 3 times it is where it use to be. I have checked the rear brake pads and they are good and at the rotor, so that is not the problem. I think I need a new rear master cylinder. Can I change it out and just bleed the rear brake? Which brake fluid, DOT 4?
Have you check the brake fluid level.
With pad wear level may have gone down a little. Carefully top off and the check. Or time to change pads?
 

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You do not state your model, but if the pre-2018; do the Rocky bleed, the normal bleed sequence plus two extra steps. Purge the old fluid while you are at it.

prs
 

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Have you check the brake fluid level.
With pad wear level may have gone down a little. Carefully top off and the check. Or time to change pads?
There is no need to "top off" the brake fluid. The fluid level in the reservoir will drop as the pads wear. This is normal. When you go to change the pads, you will need to push the pistons back into the calipers - which will push the excess fluid back into the reservoir. If you had topped off the fluid level while the pads were worn, pushing the pistons back in would result in overflowing the reservoir.

Just make sure the level doesn't get below the "low" mark on the side of the reservoir.

In fact, the more you open the reservoir, the more air you allow into the brake fluid.
 

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What year is your bike. When I had the dealer do my front forks (2002 model), they mentioned there is a recall for the rear brakes. One had been done but there was an update I need to have done. I haven't had any issues but plan to take it in when I can.
 

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Discussion Starter #7
Bike is a 2004. Nothing has been done to get air into the brake lines. probably do need to flush but I would not think that would effect pedal movement. I thinking need to replace rear master cylinder, perhaps seal(s) are not sealing unless pedal is pumped rapidly to make seals seal>
 

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Maybe check on the recall and get free master cylinder and flush out of it. Not the whole bike but the rear master and fluid change would be nice.
 

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You are eligible for a free rear master cylinder replacement with fluid flush at any authorized Honda service center. Just take your bike in and tell them you need them to fulfill the rear master cylinder brake recall.

You’re welcome.

:thumbup:
 
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Before you do anything else, do yourself a favor and compare new rear and front pads. You'll see that the rear pads are twice as thick as the front. Then figure out what steps you want to take.

Richard
 

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Discussion Starter #11
Richard- Are you saying I might need new front and rear pads? Just did not quite understand what you were suggesting.

Thanks
 

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If your brake isn't spongy but just pumps up to normal, it's a fair chance the main cup in the master cylinder is a little worn. They loose their sharp edge and just a little fluid passes by before enough pressure builds up to seal them. The act of pumping the pedal draws a little fluid from the back to the front of the seal until there's as much as there would have been had there been no leakage.
 

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I have an 02 that required rear brake bleeding every 6 months or so for years. I regularly flush and bleed the brakes and now used the Rocky bleed with significant improvement. I've not had my brake recalls done as I refuse to leave it for 7-10 days. I seriously would fully flush and bleed both front and rear brake systems, might as well do the clutch as well, its all required periodic maintenance. Lastly I found last year my rear rotor was worn to the lower limit when I changed out brake pads. I suspect the calipers were retracting just a little after use and requiring more peddle to engage the brakes as desired; my rotor looked great but was certainly due for replacement.

Sent from my Moto Z (2) using Tapatalk
 

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I'm agreeing with an earlier post. Because the rear pads are so thick, they can still be safe, but be worn enough to allow a lot of travel in the pedal. I suspect that many of the rear brake issues are the result of many owners topping off the master cylinder and then later changing pads and ending up with overfilled master cylinders.

Richard
 

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I'm agreeing with an earlier post. Because the rear pads are so thick, they can still be safe, but be worn enough to allow a lot of travel in the pedal. I suspect that many of the rear brake issues are the result of many owners topping off the master cylinder and then later changing pads and ending up with overfilled master cylinders.

Richard
Huh? That's now how hydraulic brakes work. As the pads wear (which is going to happen slowly, over time), the caliper pistons will extend, taking up the space. As this happens, more fluid will move from the master cylinder to the brake lines, but the pedal won't require any more "travel" to actuate the brakes.
 
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