Rear brake master cylinder noise. - Wrist Twisters
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post #1 of 8 Old 12-09-2019, 03:41 PM Thread Starter
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Rear brake master cylinder noise.

So my rear brake cylinder is a little noisy. At the end of its stroke as I'm applying pressure the master cylinder makes a creaking noise. Feels a little dry like it's grabbing ever so slightly. The harder I push the more noise.
Should I leave or fix? And if fix how?
Cheers fellas.

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post #2 of 8 Old 12-09-2019, 08:57 PM
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First, check the two mounting bolts for tightness, and the bolts holding the footrest bracket to the frame. Couldn't hurt.

If you haven't flushed the fluid in the last year do so! Even if you have do it again. Past that all you can do is to lube the pivots for the brake pedal and master cylinder pushrod clevis. If that doesn't cure it there may be a problem with the bore or piston, and more likely as not both. If that is the case there be parts department dragons in your near future.

удачи!

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If it has already been done, it is safe to assume it is possible to do it.
On the other hand, if it has not been done never assume it is impossible to do it.
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post #3 of 8 Old 12-09-2019, 09:32 PM Thread Starter
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Thanks Rob. All mount bolts etc are tight.
Changed brake fluid only a few months back. Master cylinder was making a creaking noise then.
It's definitely inside. I squirted some WD40 in past the bottom seal and noise went away.
I'll order some new seals and piston and pray bore is fine.

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post #4 of 8 Old 12-10-2019, 04:46 PM
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If introducing a lubricant inside the dust boot stopped the noise it is reasonable to assume the pushrod has gone dry where it engages the piston. The cure, well the more permanent cure, is to unbolt the master cylinder from the bracket and leaving the reservoir attached unbolt it as well. With the dust boot pushed back you can maneuver the master for an unobstructed view of the pushrod. Leaving the circlip in place, work some brake rubber grease into the area where the pushrod engages the piston. It won't take much and lasts for quite a while.

Rob
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If it has already been done, it is safe to assume it is possible to do it.
On the other hand, if it has not been done never assume it is impossible to do it.
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post #5 of 8 Old 12-10-2019, 04:57 PM Thread Starter
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Thanks again. I've got some red rubber grease. I'll do as you suggest.
I see in the bike manual it says to pack the sealing boot with grease.
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post #6 of 8 Old 12-10-2019, 09:16 PM
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Quote:
Originally Posted by Islandboy View Post
Thanks again. I've got some red rubber grease. I'll do as you suggest.
I see in the bike manual it says to pack the sealing boot with grease.

If it's red, I'd have suspected it might be specific for mineral based aircraft brake fluid, and not glycol based automotive fluid.
But I know you'd never get caught wrong in such a way.
So, what is red rubber grease that you have?

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post #7 of 8 Old 12-10-2019, 09:45 PM Thread Starter
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Mmmm...I hope it's the right grease. Since I did the job on my lunch break. Other than a little WD40 I spray up there the day before it was completely empty of grease. Not anymore.
I got the brake fluid and red rubber grease from my local oil man.
I'll strip the master brake cylinder apart next winter and replace all seals, spring etc. And anything else that is tired.
I was planning on using that grease on all the brake calipers at some point so I do hope it's the right stuff.
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post #8 of 8 Old 12-11-2019, 03:13 AM Thread Starter
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Castrol red rubber grease. Vegetable based.
http://www.redrubbergrease.com/

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