I'm losing this battle with the rear master cylinder

I'm losing this battle with the rear master cylinder

Postby akinz » Sat Jul 25, 2015 9:08 am

I spent hours trying to remove the rear master cylinder bits for a rebuild but man... it's past seized, I think more like welded.. air pressure, penetrating oil... no give.

Any suggestions? I'm Soooo close to being able to take this thing on its first run but I have to get this done!
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Re: I'm losing this battle with the rear master cylinder

Postby Goss » Sat Jul 25, 2015 10:14 am

Force grease through it using a grease gun, be prepared for when it pops!

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Re: I'm losing this battle with the rear master cylinder

Postby tevan » Sat Jul 25, 2015 10:22 am

Goss wrote:Force grease through it using a grease gun, be prepared for when it pops!

Regards

Goss

Get a bolt the same size that screws in where you attach the rear caliper hose and drill a hole all the way threw it and tap a zerk in it and pump the grease to it. It will push it out.
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Re: I'm losing this battle with the rear master cylinder

Postby steve murdoch icoa #5322 » Sat Jul 25, 2015 10:25 am

Have you tried boiling water and/or a heat gun on the outside of the body.
Of course the heat gun might requie a repaint.
I have also seen a method of drilling, tapping and then using a screw as a puller, obviously requiring a new piston.
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Re: I'm losing this battle with the rear master cylinder

Postby Z Grand » Sat Jul 25, 2015 12:12 pm

steve murdoch icoa #5322 wrote:I have also seen a method of drilling, tapping and then using a screw as a puller, obviously requiring a new piston.


I tried that method and still could not get the piston to budge. Sent it to a friend who used an old master cylinder and brake fluid to pump the piston out.
Here was his method:
"The first thing that had to be done was come up with a way to block off the fitting where the reservoir supplies brake fluid. That was easy - I used one of my silicone rubber plugs:
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Then I hooked up my vice-mounted master cylinder, filled it with old brake fluid, and started pumping.
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I had to occasionally crack the banjo fitting while holding the brake lever so that it would purge the air bubbles. Then I started feeling some pressure and within a minute, out popped the piston."
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Hope this helps. Of course, you'll need an old master cylinder assembly you can use for a pump.
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Re: I'm losing this battle with the rear master cylinder

Postby tevan » Sat Jul 25, 2015 3:16 pm

I made a cap out of steel where the plastic fitting was. It got sealed tight. Then the grease gun trick. :handgestures-fingerscrossed:
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Re: I'm losing this battle with the rear master cylinder

Postby daves79x » Sat Jul 25, 2015 5:26 pm

You can drill it out also, but be careful.

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Re: I'm losing this battle with the rear master cylinder

Postby akinz » Mon Jul 27, 2015 12:01 pm

Guys... Thanks so much for your help!

It came out without a problem with the grease trick!!! I used an old brake line bolt I had and drilled a hole straight though it then tapped and installed a grease fitting. Used a couple extra washers and had to cut about a half inch off the bolt so I could put it in far enough the washers would cover the brake line end of the whole.

It is now part of the CBX tool club hahaha
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Now on to blasting, painting and rebuilding :thumbsup:
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